Glossary of cellular and molecular biology (M–Z)
This glossary of cellular and molecular biology is a list of definitions of terms and concepts commonly used in the study of cell biology, molecular biology, and related disciplines, including molecular genetics, biochemistry, and microbiology. It is split across two articles:
- molecular biology (0–L) lists terms beginning with numbers and those beginning with the letters A through L.
- Glossary of cellular and molecular biology lists terms beginning with the letters M through Z.
This glossary is intended as introductory material for novices. It has been designed as a companion to Glossary of genetics and evolutionary biology, which contains many overlapping and related terms; other related glossaries include Glossary of virology and Glossary of chemistry.
M
See '.
Any very large molecule composed of dozens, hundreds, or thousands of covalently bonded atoms, especially one with biological significance. Many important, such as and, are consisting of a repeated series of smaller ; others such as and may not be polymeric but are nevertheless large and complex molecules.
The larger of the two types of which occur in pairs in the cells of some ciliated protozoa. Macronuclei are highly and responsible for directing vegetative reproduction, in contrast to the, which have important functions during.
Any of a class of relatively long-lived of the mammalian immune system which are activated in response to the presence of foreign materials in certain tissues and subsequently play important roles in antigen presentation, stimulating other types of immune cells, and killing or parasitic microorganisms, diseased cells, or tumor cells.
See '.
The branch of medicine and medical science that involves the study, diagnosis, and management of, and more broadly the application of knowledge about human to medical care.
A unit of length equal to one million in molecules or one million in duplex molecules such as.
A specialized type of that occurs exclusively in sexually reproducing eukaryotes, during which is followed by two consecutive rounds of division to ultimately produce four genetically unique daughter cells, each with half the number of as the original parent cell. Meiosis only occurs in cells of the sex organs, and serves the purpose of generating haploid such as sperm, eggs, or spores, which are later fused during fertilization. The two meiotic divisions, known as Meiosis I and Meiosis II, may also include various events between.
See '.
The of a into two, especially in the context of the.
A supramolecular aggregate of amphipathic molecules which when suspended in a polar solvent tend to arrange themselves into structures which minimize the exposure of their tails by sheltering them within a ball created by their own heads. Certain types of lipids, specifically and other, commonly occur as sheets of molecules when immersed in an aqueous environment, which can themselves assume approximately spherical shapes, acting as semipermeable barriers surrounding a water-filled interior space. This is the basic structure of the biological membranes enclosing all,, and.
Any that is closely associated either or with the surrounding a,, or.
An or enclosed by its own dedicated lipid, separating its interior from the rest of the.
Any of a class of molecules which function as molecular messengers, carrying sequence information encoded in the genome to the where protein synthesis occurs. The primary products of, mRNAs are synthesized by, which builds a chain of that complement the of a ; in this way, the DNA sequence of a protein-coding is effectively preserved in the, which is subsequently processed into a mature mRNA by a series of.
A stepwise series of biochemical reactions occurring within a cell, often but not necessarily by specific, that fulfills some activity or process related to. The reactions are linked by the sharing of reactants, products, or intermediate compounds in consecutive steps, such that the product of one reaction is used as a reactant in a subsequent reaction. Byproducts are often removed from the cell as. The overall pathway may be,, or in nature. In any actively metabolizing cell, an elaborate network of interconnected metabolic pathways is required to maintain, with degradative catabolic processes providing the energy necessary to conduct anabolic biosynthesis; for example,, the, and provide the used in fatty acid synthesis. The flux of through each pathway is regulated by the needs of the cell and the availability of.
The complete set of chemical reactions which sustain and account for the basic processes of life in all living cells, especially those involving: 1) the conversion of energy from food into energy available for cellular activities; 2) the breakdown of food into simpler compounds which can then be used as to build complex such as,, and ; and 3) the degradation and excretion of toxins, byproducts, and other unusable compounds known as. In a broader sense the term may include all chemical reactions occurring in living organisms, even those which are not strictly necessary for life but instead serve accessory functions. Many specific cellular activities are accomplished by in which one chemical is ultimately transformed through a stepwise series of reactions into another chemical, with each reaction by a specific. Most metabolic reactions can be subclassified as or.
An intermediate or end product of, especially degradative metabolism ; or any substance produced by or taking part in a metabolic reaction. Metabolites include a huge variety of small molecules generated by cells from various and having various functions, including as inputs to other pathways and reactions, as molecules, and as stimulators, inhibitors, and of. Metabolites may result from the degradation and elimination of naturally occurring compounds as well as of synthetic compounds such as pharmaceuticals.
The complete set of chemical compounds within a cell, organelle, or any other biological sample, including both molecules and molecules.
Having a positioned in the middle of the chromosome, resulting in arms of approximately equal length.
The stage of and that occurs after and before, during which the of the replicated chromosomes align along the equator of the cell, with each attached to the.
The covalent attachment of a methyl group to a chemical compound, protein, or other biomolecule, either spontaneously or by catalysis. Methylation is one of the most widespread natural mechanisms by which and are. The in a DNA molecule inhibits recognition of the methylated sequence by, which can effectively the expression of genes. Specific within are also commonly methylated, which can change positioning and similarly or nearby loci. The opposite reaction is.
Any of a class of which catalyze the covalent bonding of a methyl group to another compound, protein, or biomolecule, a process known as.
A group that "aims to provide a standard for the representation of data that would facilitate the exchange of microarray information between different data systems".
Any of a diverse class of small or found in the cells of many eukaryotes, especially plants and animals, usually having some specific metabolic function and occurring in great numbers in certain specialized cell types.,,, and are often considered microbodies.
A type of very small, generally less than 20,000 in size, present in the of some organisms.
A that is too short to cause any apparent change in morphology under a light microscope, though it may still be detectable with other methods such as.
A long, thin, flexible, rod-like structure composed of polymeric strands of proteins, usually actins, that occurs in abundance in the of eukaryotic cells, forming part of the. Microfilaments comprise the cell's structural framework. They are modified by and interact with numerous other cytoplasmic proteins, playing important roles in cell stability, motility, contractility, and facilitating changes in cell shape, as well as in.
The smaller of the two types of that occur in pairs in the cells of some ciliated protozoa. Whereas the larger is, the micronucleus is and generally transcriptionally inactive except for the purpose of sexual reproduction, where it has important functions during.
A type of small,, molecule that functions in of, particularly RNA, by base-pairing with complementary sequences in, which typically results in the cleavage or destabilization of the transcript or inhibits its by ribosomes.
A type of consisting of a relatively short of, in which certain are repeated, typically 5–50 times. Microsatellites are widespread throughout most organisms' genomes and tend to have higher mutation rates than other regions. They are classified as DNA, along with longer.
A small intracellular derived from fragments of observed in cells which have been homogenized.
See '.
An instrument used to cut extremely thin slices of material, known as microsections or simply sections, preparatory to observation under a microscope. Sections of tissues and cells are usually 50 nanometres to 100 micrometres in width. The process of cutting them is known as microtomy.
A fine protein filament of the cytoskeleton. Multiple filaments form the microtrabecular network.
Any of the long, generally straight, hollow tubes, about 24 nanometers in diameter and composed of interwoven polymeric filaments of the protein tubulin, found in the cytoplasm of many eukaryotic cells, where they are involved in maintaining the cell's shape and structural integrity as well as in force generation for cellular or locomotion. They also comprise the critical to and. Microtubules are rigid but transient all-purpose structural members which can be rapidly assembled and disassembled at the cell's needs. Many different microtubule-associated proteins interact with them. See also '.
A region near the center of a eukaryotic cell typically consisting of two oriented at right angles to each other and surrounded by a of associated proteins, which functions as the site of initiation for the assembly of.
A type of released when an evagination of the "buds off" into the extracellular space. Microvesicles vary in size from 30–1,000 nanometres in diameter and are thought to play roles in many physiological processes, including by shuttling molecules such as RNA and proteins between cells.
A small, slender, tubular cytoplasmic projection, generally 0.2–4 micrometres long and 0.1 micrometres in diameter, protruding from the surface of some animal cells and supported by a central core of. When present in large numbers, such as on cells lining the respiratory and alimentary tracts, they form a dense brush border which presumably serves to increase each cell's absorptive surface area.
The centrally constricted region that forms across the central axis of a cell during, constricted by the closing of the until the are finally separated, but occasionally persisting as a tether between the two cells for as long as a complete.
In plant cells, the outermost layer of the ; a continuous, unified layer of extracellular pectins which is the first layer deposited by the cell during and which serves to cement together the primary cell walls of adjacent cells.
A commercial standard developed by for the storage and sharing of data.
A commercial standard developed by and based on in order to facilitate the storage and sharing of data.
A region of, in which certain DNA are . In the human genome, minisatellites occur at more than 1,000 loci, especially in and, and exhibit high mutation rates and high variability between individuals. Like the shorter, they are classified as and are a type of.
See '.
See '.
An incorrect of on of or ; i.e. the presence in one strand of a duplex molecule of a base that is not complementary to the base occupying the corresponding position in the other strand, which prevents normal hydrogen bonding between the bases. For example, a paired with a would be a mismatch, as guanine normally pairs with.
A type of which results in a that codes for a different than in the unmutated sequence. Compare '.
The insertion of an incorrect in a growing chain during, i.e. the inclusion of any amino acid that is not the one specified by a particular in an transcript. Mistranslation may originate from a or from a malfunctioning.
The set of DNA molecules contained within, usually one or more circular representing a semi-autonomous which is physically separate from and functionally independent of the in the cell's nucleus. The mitochondrial genome encodes many unique enzymes found only in mitochondria.
A highly pleiomorphic found in the of nearly all eukaryotic cells, usually in large numbers in the form of sausage-shaped structures 5–10 micrometres in length, enclosed by a double membrane, with the inner membrane infolded in an elaborate series of so as to maximize surface area. Mitochondria are the primary sites of synthesis, where ATP is regenerated from via, as well as many supporting pathways, including the and the. Like other, mitochondria contain encoded in molecules which replicate independently of the, as well as their own unique set of,,,, and with which to direct transcription and translation of their genes. The majority of the found in mitochondria are encoded by nuclear genes, however, such that mitochondria are only partially autonomous. These observations suggest mitochondria evolved from symbiotic living inside eukaryotic cells.
Any substance or stimulus that promotes or induces, or more generally which causes cells to re-enter the.
The selective degradation of by means of ; i.e. the mitochondrion initiates its own degradation. Mitophagy is a regular process in healthy populations of cells by which defective or damaged mitochondria are recycled, preventing their accumulation. It may also occur in response to the changing needs of the cell, e.g. during certain developmental stages.
In cells, the part of the during which the of the takes place and replicated are separated into two distinct nuclei. Mitosis is generally preceded by the of, when the cell's, and either occurs simultaneously with or is followed by, when the and are divided into two new. Colloquially, the term "mitosis" is often used to refer to the entire process of cell division, not just the division of the nucleus.
The proportion of cells within a sample which are undergoing at the time of observation, typically expressed as a percentage or as a value between 0 and 1. The number of cells dividing by mitosis at any given time can vary widely depending on organism,, developmental stage, and media, among other factors.
The abnormal between during . during mitosis is relatively uncommon; in the laboratory, it can be induced by exposing dividing cells to high-energy electromagnetic radiation such as X rays. As in meiosis, it can separate alleles and thereby propagate potentially significant changes in zygosity to, though unless it occurs very early in development this often has little or no phenotypic effect, since any phenotypic variance shown by mutant lineages arising in terminally differentiated cells is generally masked or compensated for by neighboring cells.
The process by which most animal cells undergo an overall change in shape during or preceding, abandoning the various complex or elongated shapes characteristic of and rapidly contracting into a rounded or spherical morphology that is more conducive to. This phenomenon has been observed both ' and '.
See '.
The presence of more than one different level, i.e. more than one number of sets of, in different cells of the same cellular population.
Any genetic material that can move between different parts of a or be transferred from one species or to another within a single. The many types of MGEs include, bacterial, bacteriophage elements which integrate into host genomes by viral, and.
The complete set of within a particular, cell, species, or other taxon, including all,,, and other self-splicing nucleic acid molecules.
The branch of biology that studies biological activity at the molecular level, in particular the various mechanisms underlying the biological processes that occur in and between, including the structures, properties, synthesis, and modification of such as and, their interactions with the chemical environment and with other biomolecules, and how these interactions explain the observations of classical biology. Molecular biology relies largely on laboratory techniques of physics and chemistry to manipulate and measure microscopic phenomena. It is closely related to and overlaps with the fields of,, and.
Any of various methods designed to a particular molecule, usually a or a, many times inside the cells of a natural host. Commonly, a fragment containing a is into a, which bacterial cells are then induced to uptake in a process known as. The bacteria, carrying the recombinant plasmid, are then allowed to proliferate naturally in, so that each time the bacterial cells divide, the plasmids are replicated along with the rest of the bacterial genome. Any functioning gene of interest within the plasmid will be by the bacterial cells, and thereby its will also be cloned. The plasmids or gene products, which now exist in many copies, may then be extracted from the bacteria and purified. Molecular cloning is a fundamental tool of employed for a wide variety of purposes, often to study, to amplify a specific gene product, or to generate a.
A branch of that employs methods and techniques of to study the structure and function of and at the molecular level. Contrast '.
A set of as it exists inside the of an immature such as an ootid or spermatid, i.e. a cell which is a product of but is not yet a mature gamete.
Having only one. Contrast ' and '.
Describing cells, proteins, or molecules descended or derived from a single or made in response to a single unique compound. Monoclonal are raised against only one or can only recognize one unique on the same antigen. Similarly, the cells of some and may be described as monoclonal if they are all the asexual progeny of one original. Contrast '.
A type of large of the mononuclear phagocyte system in mammals, characterized by pale-staining cytoplasm and a kidney-shaped or horseshoe-shaped nucleus. Monocytes are derived from in bone marrow and become in other tissues.
Having a single, as opposed to or.
A molecule or compound which can exist individually or serve as a building block or of a larger aggregate known as a. Polymers form when multiple monomers of the same or similar molecular species are connected to each other by chemical bonds, either in a linear chain or a non-linear conglomeration. Examples include the individual which form polymers, the individual which form, and the individual proteins which form.
Any of a class of organic compounds which are the simplest forms of and the most basic structural subunits or from which larger carbohydrate such as,, and are composed. With few exceptions, all monosaccharides are variations on the empirical formula, where typically ranges from 3 to 7. Common examples include,, and.
The abnormal and frequently pathological presence of only one of a normal pair. It is a type of.
A synthetic connecting a short sequence of into an artificial, used in to by with sequences in naturally occurring RNA or DNA molecules, especially, thereby inhibiting interactions with other biomolecules such as proteins and. Morpholino oligomers are not themselves, and neither they nor their hybrid duplexes with RNA are attacked by ; also, unlike the negatively charged of normal nucleic acids, the synthetic backbones of Morpholinos are electrically neutral, making them less likely to interact non-selectively with a host cell's charged proteins. These properties make them useful and reliable tools for artificially generating phenotypes in living cells.
The presence of two or more populations of cells with different in an individual organism which has developed from a single fertilized egg. A mosaic organism can result from many kinds of genetic phenomena, including of chromosomes,, or mutations in individual lineages during the early development of the embryo. Mosaicism is similar to but distinct from.
Any distinctive or recurring of in a or of in a that is or is conjectured to be biologically significant, especially one that is reliably by other biomolecules or which has a that permits unique or characteristic chemical interactions such as. In nucleic acids, motifs are often short, highly which act as recognition sites for or RNAs involved in the regulation of.
Any which converts chemical energy derived from the hydrolysis of such as and into mechanical work in order to effect its own locomotion, by propelling itself along a filament or through the.
See '.
See '.
Composed of more than one. The term is used especially to describe organisms or tissues consisting of many cells descendant from the same original which work together in an organized way, but may also describe groups of nominally single-celled organisms such as protists and bacteria which live symbiotically with each other in large colonies. Contrast '.
An aggregate of two or more molecular entities, identical or non-identical, held together by non-covalent forces; e.g. a.
Having more than one within a single ; i.e. having multiple nuclei occupying the same.
The integration of data from multiple "omics" technologies in order to study complex biological relationships, discover novel associations between biological entities, pinpoint relevant, or build elaborate models of physiology and disease.
A locus or sequence within a which contains multiple unique recognized by various, which makes it possible for scientists to target the of a DNA fragment specifically to that locus and in the desired orientation, by the insert and the vector with the same endonuclease and then them together via compatible restriction ends, a technique known as. Commercial plasmids designed for cloning commonly incorporate one or more multiple cloning sites.
Any physical or chemical agent that of an organism and thereby increases the frequency of above natural background levels.
1. The process by which the genetic information of an organism is changed, resulting in a. Mutagenesis may occur spontaneously or as a result of exposure to a.
2. In, any laboratory technique by which one or more genetic mutations are deliberately in order to produce a gene, regulatory element, gene product, or so that the functions of a genetic locus, process, or product can be studied in detail.
An organism, gene product, or phenotypic resulting from a, of a type that would not be observed naturally in specimens.
Any permanent change in the of a strand of or, or in the sequence of a. Mutations play a role in both normal and abnormal biological processes; their natural occurrence is integral to the process of. They can result from errors in, chemical damage, exposure to high-energy radiation, or manipulations by. mechanisms have evolved in many organisms to correct them. By understanding the effect that a mutation has on, it is possible to establish the function of the or sequence in which it occurs.
Any mutant or sequence that increases the spontaneous of one or more other genes or sequences. Mutators are often, or may be mutant such as those that encode or proteins involved in.
A, i.e. a protein whose sequence differs from that of the normal because of a.
The smallest unit of a DNA molecule in which a physical or chemical change can result in a .
N
One of two possible orientations by which a linear DNA fragment can be inserted into a, specifically the one in which the of both fragment and vector have the same orientation. Contrast '.
See '.
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A laboratory technique involving the use of a microscopic lance or nanopipette in the presence of an electric field in order to deliver DNA or RNA directly into a cell, often a or early, via an mechanism. While submerged in a pH-buffered solution, a positive electric charge is applied to the lance, attracting negatively charged nucleic acids to its surface; the lance then penetrates the cell membrane and the electric field is reversed, applying a negative charge which repels the accumulated nucleic acids away from the lance and thus into the cell. Compare '.
In the process of being synthesized; incomplete; not yet fully processed or mature. The term is commonly used to describe of or which are actively undergoing synthesis during or, or sometimes a complete, fully transcribed RNA molecule before any have been made, or a chain actively undergoing by a.
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The inhibition or deactivation of some biological process caused by the presence of a specific molecular entity, in the absence of which the process is not inhibited and thus can proceed normally. In, for example, a repressor may bind to an upstream from a coding sequence and prevent access by and/or, thereby blocking the gene's. This is contrasted with, in which the presence of an is necessary to switch on transcription.
The of a molecule in the direction opposite to the turn of the itself. Contrast '.
See '.
A break or discontinuity in the of one of a molecule, i.e. where a is hydrolyzed but no nucleotides are removed; such a molecule is said to be nicked. A nick is a, where despite the break the DNA molecule is not ultimately broken into multiple fragments, which contrasts with a, where. Nicks may be caused by or by dedicated known as, which nick DNA at random or specific sites. Nicks are frequently placed by the cell as markers identifying target sites for enzyme activity, including in,, and, and also to release torsional stress from DNA molecules, making them important in manipulating.
Another name for a, especially one that has been artificially engineered to create single-stranded breaks by altering the cleavage activity of an endonuclease that normally creates double-stranded breaks, e.g. Cas9 nickase.
Any of a class of enzymes capable of generating a in a molecule, i.e. a, either at random or at a specific, by breaking a linking adjacent nucleotides.
Any organic compound containing a nitrogen atom that has the chemical properties of a base. –,,,, and – are especially relevant to biology because they are components of, which are the primary that make up.
Any, natural or artificial, that is not one of the 20 or 21 encoded by the. There are hundreds of such amino acids, many of which have biological functions and are specified by alternative codes or incorporated into proteins accidentally by. Many of the best known naturally occurring ncAAs occur as intermediates in the metabolic pathways leading to the standard amino acids, while others have been made synthetically in the laboratory.
Any segment of that does not a sequence that may ultimately be and into a. In most organisms, only a small fraction of the genome consists of protein-coding DNA, though the proportion varies greatly between species. Some non-coding DNA may still be transcribed into functional or may serve important developmental or purposes; other regions appear to have no known biological function.
Any molecule of that is not ultimately into a. The sequence from which a functional non-coding RNA is is often referred to as an "RNA gene". Numerous types of non-coding RNAs essential to normal genome function are produced constitutively, including,,, and ; other non-coding RNAs have no known function and are likely the product of spurious transcription.
See '.
The failure of or to properly during. Nondisjunction results in daughter cells that are, containing abnormal numbers of one or more specific. It may be caused by a variety of factors.
Broadly, any or region of a that does not contain, or in which repeats do not comprise a majority; or any segment of DNA exhibiting the expected of a unique sequence.
A type of which results in a premature in the sequence, thereby causing the premature termination of, which results in a truncated, incomplete, and often non-functional.
A factor which can inhibit the effects of a by any mechanism, usually either a mutated which can bind the mutated stop codon or some kind of mutation.
A type of in which the of one base for another results, after and, in an amino acid sequence that is different from that produced by the original unmutated gene. Because nonsynonymous mutations always result in a biological change in the organism, they are often subject to strong. Contrast '.
See '.
A method in molecular biology used to detect in a sample. Compare ', ', and '.
See '.
The end of a linear chain of that is terminated by the free amine group of the first amino acid added to the chain during. This amino acid is said to be N-terminal. By convention, sequences, domains, active sites, or any other structure positioned nearer to the N-terminus of the or the folded it forms relative to others are described as. Contrast '.
Any molecule contained within the of a eukaryotic cell, most prominently the DNA in. It is sometimes used interchangeably with.
A sub-cellular barrier consisting of two concentric that surrounds the in eukaryotic cells. The nuclear envelope is sometimes simply called the "nuclear membrane", though the structure is actually composed of two distinct membranes, an and an.
The principle that the nuclei of essentially all cells of a mature multicellular organism are genetically identical to each other and to the nucleus of the from which they descended; i.e. they all contain the same genetic information on the same chromosomes, having been replicated from the original zygotic set with extremely high fidelity. Even though all adult have the same set of genes, cells can nonetheless differentiate into distinct by different subsets of these genes. Though this principle generally holds true, the reality is slightly more complex, as mutations such as,,, and as well as,, and various types of can all cause different somatic lineages within the same organism to be genetically non-identical.
A fibrous network of proteins lining the inner, surface of the, composed of filaments similar to those that make up the. It may function as a scaffold for the various contents of the nucleus including and.
An within a which serves as a molecular signal marking the protein for into the, typically consisting of one or more short motifs containing positively charged amino acid residues exposed on the mature protein's surface. Though all proteins are in the cytoplasm, many whose primary biological activities occur inside the nucleus require nuclear localization signals identifiable by in order to cross the. Contrast '.
A mesh-like latticework of protein polymers and suspended in the in the of eukaryotic cells, akin to the in the. The nuclear matrix functions as a scaffold and an anchor for large DNA molecules such as and for the macromolecular complexes that perform essential nuclear activities such as and.
See '.
A of that creates an opening in the through which certain molecules and ions are and thereby enter or exit the . The nuclear envelope typically has thousands of pores to selectively regulate the exchange of specific materials between the and the, including, which are transcribed in the nucleus but must be translated in the cytoplasm, as well as, which are synthesized in the cytoplasm but must return to the nucleus to serve their functions.
Any that is naturally found in or to the cell's .
Any molecule located within a cell's, whether associated with chromosomes or existing freely in the nucleoplasm, including,, and all newly transcribed, or, prior to their export to the cytosol.
The mechanisms by which molecules cross the surrounding a cell's nucleus. Though small molecules and ions can cross the membrane freely, the entry and exit of larger molecules is tightly regulated by, so that most such as RNAs and proteins require association with transport factors in order to be across.
Any of a class of capable of cleaving connecting adjacent in a nucleic acid molecule. Nucleases may or strands of a duplex molecule, and may cleave randomly or at specific recognition sequences. They are ubiquitous and imperative for normal cellular function, and are also widely employed in laboratory techniques.
A long, made up of smaller called which are chemically linked to one another in a chain. Two specific types of nucleic acid, and, are common to all living organisms, serving to encode the genetic information governing the construction, development, and ordinary processes of all biological systems. This information, contained within the order or, is into, which direct all of the chemical reactions necessary for life.
The precise order of consecutively linked in a molecule such as or. Long sequences of nucleotides are the principal means by which biological systems store genetic information, and therefore the accurate,, and of such sequences is of the utmost importance, lest the information be lost or corrupted. Nucleic acid sequences may be equivalently referred to as sequences of nucleotides,,, or, in,, and they correspond directly to sequences of and.
Any of the five primary or canonical –,,,, and – that form and, the latter of which are the fundamental building blocks of. The ability of these bases to form via hydrogen bonding, as well as their flat, compact three-dimensional profiles, allows them to "stack" one upon another and leads directly to the long-chain structures of and. When writing sequences in shorthand notation, the letter N is often used to represent a nucleotide containing a generic or unidentified nucleobase.
An irregularly shaped region which contains most or all of the genetic material in prokaryotic cells such as bacteria, but is not enclosed by a as in eukaryotes.
The primary of which the eukaryotic is composed, thought to play important roles in decondensation, transcription of, and assembly.
The central region of the, composed of dense, convoluted fibrillar material.
An within the of eukaryotic cells which is composed of proteins, DNA, and RNA and serves as the site of synthesis.
All of the material enclosed within the of a cell by the, analogous to the enclosed by the main. Like the cytoplasm, the nucleoplasm is composed of a gel-like substance in which various,, and other are suspended, including nuclear DNA in the form of, the,, and free.
Any that is chemically bonded to or conjugated with a. Examples include,, and many.
Any of a class of which catalyze the decomposition of into their component and sugars.
An organic molecule composed of a bonded to a . A additionally includes one or more.
The soluble, liquid portion of the .
The basic structural subunit of used in nuclear DNA such as chromosomes, consisting of a proteins around which is wrapped in a manner akin to thread wound around a spool. The technical definition of a nucleosome includes a segment of DNA about 146 base pairs in length which makes 1.67 left-handed turns as it coils around the histone core, as well as a stretch of connecting it to an adjacent core particle, though the term is often used to refer to the core particle alone. Long series of nucleosomes are further condensed by association with histone H1 into higher-order structures such as and ultimately . Because the histone–DNA interaction limits access to the DNA molecule by other proteins and RNAs, the precise positioning of nucleosomes along the DNA sequence plays a fundamental role in controlling whether or not genes are and, and hence mechanisms for moving and ejecting nucleosomes have evolved as a means of the expression of particular loci.
A region of a genome or chromosome in which long segments of DNA are bound by few or no, and thus exposed to manipulation by other proteins and molecules, especially implying that the region is active.
Any of a class of phosphoric monoester hydrolase which catalyze the hydrolysis of a into a and. Such enzymes may or may not distinguish from, i.e. their function may not be sugar-specific.
An organic molecule that serves as the fundamental or subunit of polymers, including and. Each nucleotide is composed of three connected functional groups: a, a, and a single. Though technically distinct, the term "nucleotide" is often used interchangeably with nitrogenous base,, and when referring to the that make up nucleic acids. Compare '.
See '.
A large spherical or lobular surrounded by a which functions as the main storage compartment for the genetic material of eukaryotic cells, including the DNA comprising, as well as the site of RNA synthesis during. The vast majority of eukaryotic cells have a single nucleus, though some cells may have, either temporarily or permanently, and in some organisms there exist certain cell types which lose their nuclei upon reaching maturity, effectively becoming. The nucleus is one of the defining features of eukaryotes; the cells of prokaryotes such as bacteria lack nuclei entirely.
O
See '.
One of three used in the ; in, it is specified by the nucleotide triplet. The other two stop codons are named and.
of which are synthesized discontinuously by and later linked together by to create the during. Okazaki fragments are the consequence of the unidirectionality of DNA polymerase, which only works in the 5' to 3' direction.
A short, consisting of a sequence of repeating nucleotides. Oligo dTs are commonly to be used as primers for in vitro reactions during techniques, where short chains of 12 to 18 thymine bases readily complement the of, allowing the selective amplification and preparation of a from a pool of coding transcripts.
Any molecule consisting of a relatively short series of connected or ; e.g. an is a short series of nucleotides.
A relatively short chain of . In the laboratory, oligonucleotides are commonly used as or to detect the presence of larger molecules or assembled into two-dimensional microarrays for analysis.
A molecule consisting of a relatively short chain of connected. Oligosaccharides have important functions in processes such as and. Longer chains are called.
A suffix used to describe any of the diverse fields of study that conduct rigorous, systematic analyses of any of the "omes", e.g. the,,,, etc., each of which represents the totality of a specific class of biological content that has been or could hypothetically be isolated from an individual cell, population of cells, organism, species, or some other particular context. Thus is the field of study which analyzes the totality of genes in a genome, studies the complete set of all of the proteins in a proteome, etc. The term may also be used to refer to all of these fields collectively.
A that has the potential to cause cancer. In tumor cells, such genes are often and/or at abnormally high levels.
The hypothesis that there exists a large class of in which each particular gene directs the synthesis of one particular or. Historically it was thought that all genes and proteins might follow this rule by definition, but it is now known that many proteins are composites of different polypeptides and therefore the product of multiple genes, and also that some genes do not encode polypeptides at all but instead produce, which are never translated.
One of three used in the ; in, it is specified by the nucleotide triplet. The other two stop codons are named and.
See '.
The part of a that has the ability to be from DNA or RNA into protein; any continuous stretch of that contains a and a.
A sequence within an, typically located between the sequence and the of the operon, to which an uninhibited protein can bind, thereby physically obstructing from initiating the of adjacent cistrons.
A functional unit of consisting of a cluster of neighboring which are collectively under the control of a single, along with one or more adjacent sequences such as. The set of genes is together, resulting in a single molecule encoding multiple distinct polypeptides which may then be together or undergo to create multiple mRNAs which are translated independently; the result is that the genes contained in the operon are either expressed together or not at all. Regulatory proteins, including and, usually bind specifically to the regulatory sequences of a given operon; by some definitions, the genes that code for these regulatory proteins are also considered part of the operon.
Any substance, especially certain blood-serum proteins such as, that in binding to the surface of foreign cells or particulate matter increases the susceptibility of the foreign material to by. Opsonins work by linking foreign particles to specific on the surface of phagocytic cells in a process known as opsonization.
A spatially distinct compartment or subunit within a which has a specialized function. Organelles occur in both prokaryotic and eukaryotic cells. In the latter they are often separated from the by being enclosed with their own, though organelles may also be functionally specific areas or structures without a surrounding membrane; some cellular structures which exist partially or entirely outside of the cell membrane, such as and, are also referred to as organelles. There are numerous types of organelles with a wide variety of functions, including the various compartments of the,,,,, and, among others. Many organelles are unique to particular cell types or species.
A particular location within a DNA molecule at which is initiated. Origins are usually defined by the presence of a particular replicator sequence or by specific chromatin patterns.
Physiological dysfunction caused by a sudden change in the concentration of dissolved solutes in the environment surrounding a cell, which provokes the rapid movement of water across the by, either into or out of the cell. In a severely environment, where extracellular solute concentrations are extremely high, osmotic pressure may force large quantities of water to move out of the cell, leading to its desiccation; this may also have the effect of inhibiting transport of solutes into the cell, thus denying it the substrates necessary to sustain normal cellular activities. In a severely environment, where extracellular solute concentrations are much lower than intracellular concentrations, water is forced to move into the cell, causing it to swell in size and potentially burst, or triggering.
A sequence near the of a that is removed by a special form of during. Outrons are located entirely outside of the transcript's, unlike.
An abnormally high level of which results in an excessive number of copies of one or more. Overexpression produces a pronounced gene-related.
The process by which cells use chemical energy obtained by the oxidation of nutrients to power the production of . Oxidative phosphorylation couples two related processes: in the, a series of enzyme-catalyzed redox reactions transfers electrons from energetic donors such as and through various intermediates and ultimately to a terminal electron acceptor such as molecular oxygen ; the energy liberated by these reactions is simultaneously used in to move protons across a membrane and against their concentration gradient, generating an electrochemical potential which powers, an enzyme that catalyzes the of into ATP. In eukaryotes, both of these processes are carried out by proteins embedded in the membranes of and ; in prokaryotes, they occur in the cell membrane.
The flow of oxygen from environmental sources to the of a cell, where oxygen atoms participate in biochemical reactions that result in the oxidation of energy-rich substrates such as in a process known as.
P
A class of regulatory proteins encoded by the TP53 gene in vertebrates which and in order to protect the genome from mutation and block progression through the if DNA damage does occur. It is mutated in more than 50% of human cancers, indicating it plays a crucial role in preventing cancer formation.
In, the third of five substages of, following and preceding. During pachynema, the facilitates between the synapsed, and the begin to move apart from each other.
A of a double-stranded or molecule in which the unidirectional sequence of on one strand is identical to the sequence in the same direction on the strand. In other words, a sequence is said to be palindromic if it is equal to its own. Palindromic are common for.
The transfer of substances across an by passing through the space between cells, in contrast to, where substances travel through cells by crossing the cytoplasm.
Describing or relating to a class of agonist molecules produced and secreted by regulatory cells into the extracellular environment and then transported by passive diffusion to target cells other than those which produced them. The term may refer to the molecules themselves, sometimes called paramones, to the cells that produce them, or to signaling pathways which rely on them. Compare ', ', and '.
An idiotope, i.e. the specific site or region within an that recognizes and binds to a particular or. The uniqueness of a paratope allows it to bind to only one epitope with very high affinity. At the end of each arm of the Y-shaped antibody is an identical paratope, and each paratope comprises a total of six which protrude from a series of antiparallel in the antibody's higher structure. The term is also sometimes used to refer to the specific site on a molecule which defines the ligand's specificity for other molecules such as.
The original or ancestral cell from which a given set of descendant cells, known as, have divided by or.
A DNA fragment of interest designed to be into a 'vehicle' such as a and then.
The movement of a solute across a by traveling down an electrochemical or concentration gradient, using only the energy stored in the gradient and not any energy from external sources. Contrast '.
A phenomenon observed in cells, including animal tissues and many microorganisms such as yeast, whereby the presence of oxygen in the environment inhibits the cell's use of ethanol pathways to generate energy, and drives the cell to instead make use of the available oxygen in ; or more generally the observed decrease in the rate of or of lactate production in cells exposed to oxygenated air.
See '.
See '.
Any containing five carbon atoms. The compounds and are both pentose sugars, which, in the form of cyclic five-membered rings, serve as the central structural components of the and that make up and, respectively.
See '.
A short chain of linked by covalent. Peptides are the fundamental building blocks of longer chains and hence of.
A covalent chemical bond between the of one and the of an adjacent amino acid, formed by a dehydration reaction catalyzed by, an enzyme within the, during. A linear chain of amino acids linked by peptide bonds may be called a or.
A glycoconjugate complex of interwoven peptides and polysaccharides that is a primary constituent of the in all bacteria and archaea, consisting of strands of glycosaminoglycans by short to form a rigid lattice of indefinite size. The proportion of the cell wall that is peptidoglycan varies widely by strain and is often used to aid strain identification: the higher peptidoglycan content of the cell walls of Gram-positive bacteria causes them to a darker color than Gram-negative bacteria.
The space between the and of the.
Any of a class of which attach only temporarily to the, either by penetrating the or by attaching to which are permanently embedded within the membrane. The ability to reversibly interact with membranes makes peripheral membrane proteins important in many different roles, commonly as regulatory of and. Their often undergo rearrangement, dissociation, or when they interact with the membrane, resulting in the activation of their biological activity. In, peripheral membrane proteins are typically more water-soluble and much easier to isolate from the membrane than.
In a bacterial cell, the space between the and the.
A small found in many eukaryotic cells which specializes in carrying out oxidative reactions with various enzyme peroxidases and catalase, generally to mitigate damage from reactive oxygen species but also as a participant in various such as of fatty acids.
1. The tendency of a to continue moving in the same direction as previously; that is, even in isotropic environments, there inevitably still exists an inherent bias by which, from instant to instant, cells are more likely not to change direction than to change direction. Averaged over long periods of time, however, this bias is less obvious and cell movements are better described as a.
2. The ability of some viruses to remain present and viable in cells, organisms, or populations for very long periods of time by any of a variety of strategies, including retroviral integration and immune suppression, often in a latent form which replicates very slowly or not at all.
A shallow, transparent plastic or glass dish, usually circular and covered with a lid, which is widely used in biology laboratories to hold solid or liquid for the purpose of. They are particularly useful for, where they provide a flat, sterile surface conducive to colony formation from which scientists can easily isolate and identify individual colonies.
A with a genome encoding a mobile that can be by co-infection of the host cell with a. Phagemids are useful as vectors for library production.
Any cell capable of, especially any of various cell types of the immune system which engulf and ingest harmful foreign molecules, bacteria, and dead or dying cells, including and.
The process by which foreign cells, molecules, and small particulate matter are engulfed and ingested via by specialized cells known as .
A large, intracellular, membrane-bound formed as a result of and containing whatever previously extracellular material was engulfed during that process.
The study of the role played by the in the body's response to pharmaceutical drugs, combining the fields of pharmacology and.
The complete set of that are or can be expressed by a, cell, tissue, organism, or species; the sum of all of its manifest chemical, morphological, and behavioral characteristics or traits.
A delay in the of a genetic owing to the time required for the manifestation of changes in the affected biochemical pathways.
The composite of the observable morphological, physiological, and behavioral of an organism that result from the of the organism's as well as the influence of environmental factors and the interactions between the two.
A type of phenotypic plasticity in which a cell rapidly undergoes major changes to its morphology and/or function, usually via modifications, allowing it to quickly switch back and forth between disparate phenotypes in response to changes in the local microenvironment.
Any of a class of that catalyze the hydrolytic cleavage of a phosphoric acid monoester into a ion and an alcohol, e.g. the removal of a phosphate group from a via the breaking of the connecting the phosphate to a or sugar or to another phosphate, a process termed. The is performed by.
Any chemical species or functional group derived from phosphoric acid by the removal of one or more protons ; the completely ionized form,, consists of a single, central phosphorus atom covalently bonded to four oxygen atoms via three single bonds and one double bond. Phosphates are abundant and ubiquitous in biological systems, where they occur either as free anions in solution, known as inorganic phosphates and symbolized Pi, or bonded to organic molecules via ester bonds. The huge diversity of organophosphate compounds includes all, whose phosphate groups are linked by to form the of such as and, and the high-energy diphosphate and triphosphate substituents of individual nucleotides such as and serve as essential energy carriers in all cells. are major components of most. Enzymes known as and catalyze the and of phosphate groups to and from these and other biomolecules.
The linear chain of alternating and sugar compounds that results from the linking of consecutive in the same of a molecule, and which serves as the structural framework of the nucleic acid. Each individual strand is held together by a repeating series of connecting each to the or sugars of two adjacent nucleotides. These bonds are created by and broken by.
A pair of ester bonds linking a molecule with the two rings of consecutive on the same strand of a. Each phosphate forms a covalent bond with the of one pentose and the of the adjacent pentose; the repeated series of such bonds that holds together the long chain of nucleotides comprising and molecules is known as the.
Any of a subclass of consisting of a central alcohol covalently bonded to three functional groups: a negatively charged group, and two long chains. This arrangement results in a highly amphipathic molecule which in aqueous solutions tends to aggregate with similar molecules in a lamellar or micellar conformation with the phosphate "heads" oriented outward, exposing them to the solution, and the fatty acid "tails" oriented inward, minimizing their interactions with water and other polar compounds. Phospholipids are the major structural in almost all biological except the membranes of some plant cells and, where dominate instead.
See '.
The attachment of a ion,, to another molecule or ion or to a by covalent bonding. Phosphorylation and the inverse reaction,, are essential steps in numerous biochemical pathways, including in the production of ; in the metabolism of and the synthesis of ; and in the of amino acid residues in many proteins. which catalyze phosphorylation reactions are known as ; those that catalyze dephosphorylation are known as.
A form of in which liquid and suspended solids from the environment are captured in inward of the which then "bud off" into enclosed in the. The contents of these vesicles are then passed to organelles such as by fusion of the vesicular and organellar membranes. Pinocytosis is the predominant form of endocytosis occurring in most cells, such that the term is often used interchangeably with endocytosis as a whole.
See '.
The number of contained within a single complete turn of the, used as a measure of the "tightness" or density of the helix's spiral.
See '.
Any small molecule that is physically separated from the larger body of and can independently. Plasmids are typically small,, molecules in such as bacteria, though they are also sometimes present in archaea and.
The process by which which have been inside a are distributed equally between during.
The development of resistance to toxins or antibiotics which is enabled by the of encoded within small, independently replicating DNA molecules known as. This process occurs naturally via mechanisms such as, but is also a common aspect of methods such as.
The temporary shrinkage of the of a plant or bacterial cell away from the, caused by loss of water from the cell.
Any of a class of found in the cells of some eukaryotes such as plants and algae which are hypothesized to have evolved from endosymbiotic cyanobacteria; examples include, chromoplasts, and leucoplasts. Plastids retain their own which replicate independently of the host cell's genome. Many contain photosynthetic pigments which allow them to perform, while others have been retained for their ability to synthesize unique chemical compounds.
1. Variability in the size, shape, or of cells and/or their nuclei, particularly as observed in and, where morphological variation is frequently of a cellular abnormality such as disease or.
2. In microbiology, the ability of some microorganisms such as certain bacteria and viruses to alter their morphology, metabolism, or mode of reproduction in response to changes in their environment.
The tendency of cells within a to migrate in the direction of the local highest tension or maximal principal stress, exerting minimal shear stress on neighboring cells and thereby propagating the tension across many intercellular junctions and causing the cells to exhibit a sort of collective migration.
The number of complete sets of in a cell, and hence the number of possible present within the cell at any given locus.
See '.
A by which a single base is changed,, or from a of DNA or RNA.
A consisting of a chain of repeated residues, 40–250 nucleotides in length, attached to the of nearly all mature eukaryotic transcripts.
The addition of a series of multiple, known as a, to the of a, typically a. Primary transcripts are first cleaved 10–30 nucleotides downstream of a highly conserved sequence, then the poly tail is generated from the chaining of multiple molecules through the action of polynucleotide adenylyltransferase. A class of, polyadenylation serves different purposes in different cell types and organisms. In eukaryotes, the addition of a poly tail is an important step in the processing of a raw transcript into a mature mRNA, ready for export to the cytoplasm where occurs; in many bacteria, polyadenylation has the opposite function, instead promoting the RNA's degradation.
Describing cells, proteins, or molecules descended or derived from more than one or made in response to more than one unique stimulus. are often described as polyclonal if they have been produced or raised against multiple distinct or multiple variants of the same antigen, such that they can recognize more than one unique. Contrast '.
See '.
A composed of multiple repeating or ; a chain or aggregation of many individual molecules of the same compound or class of compound. The formation of polymers is known as and generally only occurs when sites are present and the concentration of monomers is sufficiently high. Many of the major classes of are polymers, including and.
Any of a class of which catalyze the synthesis of molecules, especially polymers, typically by encouraging the of free with those of an existing strand. and are essential for and, respectively.
Any of a wide variety of molecular biology methods involving the rapid production of millions or billions of copies of a specific, allowing scientists to selectively fragments of a very small sample to a quantity large enough to study in detail. In its simplest form, PCR generally involves the incubation of a target DNA sample of known or unknown sequence with a reaction mixture consisting of, a heat-stable, and free, all of which are supplied in excess. This mixture is then alternately heated and cooled to pre-determined temperatures for pre-determined lengths of time according to a specified pattern which is repeated for many cycles, typically in a which automatically controls the required temperature variations. In each cycle, the most basic of which includes a phase, phase, and phase, the copies synthesized in the previous cycle are used as for synthesis in the next cycle, causing a chain reaction that results in the exponential growth of the total number of copies in the reaction mixture. Amplification by PCR has become a standard technique in virtually all molecular biology laboratories.
The formation of a from its constituent ; the chemical reaction or series of reactions by which monomeric are covalently linked together into a polymeric chain or branching aggregate; e.g. the polymerization of a chain by linking consecutive, a reaction catalyzed by a enzyme.
1. In genetics, the regular and simultaneous existence of two or more discontinuous or genotypes in the same population where the frequency of each allele is greater than can be explained by recurrent mutation alone, typically occurring in more than 1 percent of the population's individuals. An example is the different human blood types.
2. In chemistry, the existence of the same substance in two or more different crystalline forms.
A long, continuous, and unbranched chain of linked by covalent, typically longer than a. generally consist of one or more polypeptides or arranged in a biologically functional way.
Having more than two homologous copies of each ; i.e. any level that is greater than. Polyploidy may occur as a normal condition of chromosomes in certain cells or even entire organisms, or it may result from errors in or mutations causing the duplication of the entire chromosome set.
See '.
A linear or branched chain of . Examples include and cellulose.
A functional unit of consisting of multiple attached along the length of the same transcript.
The condition of a cell or organism having at least one more copy of a particular than is normal for its level, e.g. a organism with three copies of a given chromosome is said to show. Every polysomy is a type of.
Any effect on the or functionality of a or sequence that is a consequence of its location or position within a or other DNA molecule. A sequence's precise location relative to other sequences and structures tends to strongly influence its activity and other properties, because different on the same molecule can have substantially different and physical/chemical environments, which may also change over time. For example, the of a gene located very close to a,, or is often or entirely prevented because the proteins that make up these structures block access to the DNA by, while the same gene is transcribed at a much higher rate when located in. Proximity to,, and other, as well as to regions of frequent by, can also directly affect expression; being located near the end of a chromosomal arm or to common points may affect when occurs and the likelihood of. Position effects are a major focus of research in the field of.
A strategy for identifying and a based on knowledge of its or position alone and with little or no information about its or function, in contrast to. This method usually begins by comparing the genomes of individuals expressing a of unknown provenance and identifying shared between them. Regions defined by markers flanking one or more are cloned, and the genes located between the markers can then be identified by any of a variety of means, e.g. by the region and looking for, by comparing the sequence and expression patterns of the region in and individuals, or by testing the ability of the putative gene to a mutant phenotype.
See '.
The initiation, activation, or enhancement of some biological process by the presence of a specific molecular entity, in the absence of which the process cannot proceed or is otherwise diminished. In, for example, the binding of an activating molecule such as a to a may recruit to a coding sequence, thereby causing it to be. Contrast '.
The of a molecule in the same direction as the turn of the itself. Contrast '.
A partially differentiated or intermediate with the ability to further differentiate into only one ; i.e. a stem cell that is the immediate parent cell from which fully differentiated cell types divide. The term "precursor cell" is sometimes used interchangeably with, though this term may also be considered technically distinct.
The unprocessed, single-stranded molecule produced by the of a sequence as it exists before such as convert it into a mature RNA product such as an,, or. A precursor mRNA or pre-mRNA, for example, is a primary transcript which, after processing, becomes a mature mRNA ready for.
Any of a class of enzymes that catalyze the synthesis of short, ~10-base, which by complementing the during are used as by to initiate the synthesis of.
A short,, typically 5–100 bases in length, which "primes" or initiates nucleic acid synthesis by to a complementary sequence on a and thereby providing an existing from which a can the new strand. Natural systems exclusively use primers to initiate and some forms of prokaryotic, whereas the ' syntheses performed in many laboratory techniques such as often use primers. In modern laboratories, primers are carefully designed, often in "forward" and "reverse" pairs, to complement specific and unique sequences in target DNA molecules, with consideration given to their and temperatures, and then purchased from commercial suppliers which create oligonucleotides on demand by.
The initiation of synthesis by the or of one or more to a complementary sequence within a.
See '.
An inactive precursor of a or that is converted into the active form by some, such as by cleaving a specific peptide sequence from the precursor or by attaching other molecules to specific amino acid residues. The names of protein precursors are often prefixed with pro-, as in proinsulin. Enzyme precursors may be called.
Any reagent used to make a single measurement in a biochemical assay such as a gene expression experiment. Molecules which have a specific affinity for one or more other molecules may be used to probe for the presence of those other molecules in samples of unknown composition. Probes are often or otherwise used as to indicate whether or not a specific chemical reaction is taking place. See also '.
A collection of two or more designed to measure a single molecular species, such as a collection of designed to to various parts of the transcripts generated from a single gene.
An alternative definition of a which emphasizes the contribution of non-DNA factors to the process by which the information encoded in a results in the synthesis of a.
The second stage of in, following and preceding, during which the disintegrates, the inside form around their, emerging from the poles of the reach the nuclear space and attach to the kinetochores, and associated with the microtubules begin to push the chromosomes toward the center of the cell.
A sequence or region of DNA, usually 100–1,000 base pairs long, which the of one or more associated by containing binding sites for which recruit to the sequence and initiate. Promoters are typically located immediately of the genes they regulate, near to and often including the.
See '.
The first stage of in both and, occurring after and before, during which the DNA of the chromosomes is into, the disintegrates, move to opposite ends of the cell, and the forms.
Any of a class of which catalyze, i.e. the decomposition of proteins into smaller polypeptides or individual amino acids, by cleaving via hydrolysis. Proteases are ubiquitous components of numerous, and therefore it is often necessary to inhibit them in order for laboratory techniques involving protein activity to be effective.
A large of enzymes that selectively degrades intracellular proteins which have been for degradation by. Proteasomes play important roles in the timing and onset of cellular processes through the signal-mediated of certain enzymes and regulatory proteins; they also contribute to the stress response by removing abnormal proteins and to the immune response by generating peptides.
A composed of one or more of linked by. Proteins are the three-dimensional structures created when these chains into specific higher-order arrangements following, and it is this folded structure which determines a protein's chemical activity and hence its biological function. Ubiquitous and fundamental in all living organisms, proteins are the primary means by which the activities of life are performed, participating in the vast majority of the biochemical reactions that occur inside and outside of cells. They are often classified according to the type of reaction they facilitate or catalyze, by the chemical substrate they act upon, or by their functional role in cellular activity; e.g. as,,,, or links within.
An assembly or aggregate of multiple held together by intermolecular forces, especially one with a particular biological function. Complexes may include many of the same protein or all different proteins. Numerous cellular activities, including,, and, rely on protein complexes.
The physical process by which the linear chains of amino acids synthesized during are changed from random coils into stable, orderly, three-dimensional shapes by assuming a higher-order structure or which permits the protein to be biologically functional, known as its. Folding is the consequence of amino acid residues participating in intermolecular electrostatic interactions with each other and with their surroundings, including other molecules, and so is strongly influenced by the particularities of the local chemical environment. The time it takes to properly fold a protein can vary greatly, but the process often begins while chain synthesis is still ongoing. Some chains may have or which and remain unfolded across a wide range of chemical conditions. Having the correct three-dimensional structure is essential for proper protein function, and misfolded proteins are generally biologically inactive, though mutant folds can occasionally modify functionality in useful ways.
Any of a class of enzymes which proteins by catalyzing the transfer of a from to an amino acid residue and often causing a functionally relevant as a result. The great majority of protein kinases phosphorylate the hydroxyl side chains of either serine, threonine, or tyrosine, though other types also exist. Separate classes of phosphorylate non-protein molecules such as lipids and carbohydrates.
The set of biological mechanisms by which are directed and transported to appropriate destinations within or outside of the cell. Proteins must often be routed into the interior of, embedded, or into the extracellular environment in order to serve their functions, and information contained in the protein itself instructs this delivery process. In eukaryotic cells, an expansive network of organelles and is specialized to facilitate protein sorting, including the and the.
See '.
A containing a which can be transcribed and translated to produce a, as opposed to an, which produces transcripts that are not translated into proteins but instead have functions in and of themselves.
Any of the 20 canonical which are encoded by the and incorporated into and ultimately during. The term may also be inclusive of an additional two amino acids encoded by non-standard which can be incorporated by special translation mechanisms.
Any heavily, i.e. a core polypeptide with one or more covalently attached glycosaminoglycan chains. Proteoglycans are therefore considered a subclass of in which the carbohydrate units are long, linear polymers containing amino sugars and generally bearing a net negative charge under physiological conditions due to the presence of sulfates and uronic acid groups. They are a major component of the between animal cells, where they form large hydrated complexes commonly employed in connective tissues such as cartilage.
The decomposition of into their component or individual by the linking the amino acids together via hydrolysis. Proteolysis is an important reaction used not only for degrading and inactivating proteins but sometimes also to activate them by removing amino acid residues which inhibit their activity. It is usually catalyzed by known as.
The entire set of that is or can be by a particular, cell, tissue, or species at a particular time or under particular conditions.
The study of the of a particular genome, cell, or organism, i.e. the sum total of all of the produced from it by. Proteomics technologies allow scientists to and identify proteins and and determine which ones are most and least abundant at a given time or under a given experimental condition.
Any molecular subunit from which a larger is built, including those subunits which are not strictly and can themselves be divided into subunits. For example, a of tubulin proteins is the protomer for assembly.
See .
The biological contents enclosed within a space, variously referring to the, or the cytoplasm and considered collectively, and sometimes exclusive of.
A plant, fungal, or bacterial cell which has had its removed by mechanical, chemical, or enzymatic means; or the complete contents of an intact cell excluding the cell wall.
The of substances from a cell, organelle, or tissue in a regular, rhythmic, pulse-like pattern. Many molecules such as and are released in this manner in order to maintain or to sensitize target cells by stimulating their production of.
A double-ringed heterocyclic organic compound which, along with, is one of two molecules from which all are derived. and are classified as purines. The letter is sometimes used to indicate a generic purine; e.g. in a nucleotide sequence read, may be used to indicate that either purine nucleobase, or, can be substituted at the indicated position.
A specific suspected to be a functional based on the identification of its. The gene is said to be "putative" in the sense that no function has yet been described for its.
The irreversible condensation of inside the as the cell undergoes or, resulting in a compact mass which strongly and is conspicuous under a microscope. It is followed by.
A single-ringed heterocyclic organic compound which, along with, is one of two molecules from which all are derived.,, and are classified as pyrimidines. The letter is sometimes used to indicate a generic pyrimidine; e.g. in a nucleotide sequence read, may be used to indicate that either pyrimidine nucleobase –,, or – can be substituted at the indicated position.
A type of caused by photochemical damage to or, whereby exposure to ultraviolet radiation induces the formation of covalent bonds between occupying adjacent positions in the same polynucleotide, which in turn may cause local conformational changes in and prevent with the opposite strand. In DNA, the dimerization reaction occurs between neighboring and residues ; it can also occur between cytosine and residues in. Pyrimidine dimers are usually quickly corrected by, but uncorrected lesions can inhibit or arrest polymerase activity during or.
Q
A in which there is little or no active cell growth or replication but in which the cells nonetheless continue to survive, as observed with some cultures.
R
A popular description of the path followed by a or particle when there is no bias in movement, i.e. when the direction of movement at any given instant is not influenced by the direction of movement in the preceding instant. The essential randomness of cell movement in a uniform environment is only apparent over long periods of time, however; in the short term, cells can and do exhibit.
1. An abbreviation of.
2. An abbreviation of.
A way of dividing the in a or molecule into a series of consecutive, non-overlapping groups of three nucleotides, known as, which is how the sequence is interpreted or "read" by during. In, each triplet is referred to as a and corresponds to a particular to be added to the nascent peptide chain during translation. In general, only one reading frame in a given sequence encodes a functional protein, though there are exceptions. A results in a shift in the normal reading frame which affects all downstream codons and usually results in a completely different and senseless amino acid sequence.
The continued or of a DNA or mRNA sequence, respectively, beyond encoded termination signals such as a sequence or a.
See '.
The measurement and manipulation of the rate of of strands of, generally by heating and denaturing a molecule into and then observing their rehybridization at a cooler temperature. Because the + requires more energy to anneal than the base pair +, the rate of reannealing between two strands depends partly on their, and it is therefore possible to predict or estimate the sequence of the duplex molecule by the time it takes to fully hybridize. Reassociation kinetics is studied with : fragments reannealing at low C0t values tend to have highly, while higher C0t values imply more unique sequences.
A which initiates a cellular response to an external stimulus or by binding a specific, often a dedicated signaling molecule. Numerous types of receptors exist which serve an enormous variety of functions., such as those that bind acetylcholine and insulin, are embedded within the with their exposed to the extracellular space; intracellular receptors, including many receptors, are located in the cytoplasm, where they bind ligands that have diffused across the membrane and into the cell.
A type of by which there is a reciprocal exchange of chromosome segments between two or more non-. When the exchange of material is evenly balanced, reciprocal translocations are usually harmless.
A specific or, either of nucleotides in a nucleic acid molecule or of amino acids in a protein, that is "recognized" or identified by another protein in order to direct the protein's activity to a specific molecule or location. Recognition motifs may consist of a simple consecutive sequence within a single molecule or may involve multiple non-consecutive motifs, e.g. amino acids in separate parts of the same polypeptide which are brought into juxtaposition by the created during. Recognition sites often help to distinguish the nucleic acid or protein bearing the motif from other similar molecules and thereby identify it as a valid target for some biochemical activity, or to specify a locus or subregion within the larger macromolecule at which the activity is to occur. In this sense recognition sites are critical for properly localizing proteins to their biochemical targets. A protein's recognition site is often but not necessarily the same as its or.
Any molecule in which laboratory methods of have brought together genetic material from multiple sources, thereby creating a that would not otherwise be found in a naturally occurring genome. Because DNA molecules from all organisms share the same basic chemical structure and properties, DNA sequences from any species, or even sequences created de novo by, may be incorporated into recombinant DNA molecules. Recombinant DNA technology is widely used in.
Any of a class of united by their ability to catalyze some form of, by any of a variety of mechanisms, e.g. by.
See ', ', and '.
Any that increases the likelihood of in nearby regions of the genome, e.g. the Chi sequence in certain species of bacteria.
The smallest unit of a DNA molecule capable of undergoing, i.e. a pair of consecutive nucleotides, adjacent to each other in '.
A group of non-contiguous which are as a unit, generally by virtue of having their controlled by the same regulatory element or set of elements, e.g. the same or. The term is most commonly used with prokaryotes, where a regulon may consist of genes from multiple.
Any pattern of within a which occurs in multiple copies in the same nucleic acid molecule such as a chromosome or within a genome. Repeated sequences are classified according to their length, structure, location, mode of replication, or evolutionary origin. They may be any length, but are often short of less than 100 bases; they may be or, and may occur in with the copies immediately adjacent to each other or with non-repeated sequences. Significant fractions of most eukaryotic genomes consist of, much of it retroviral in origin, though repeats may also result from errors in normal cellular processes, as with during or. Because so many genetic mechanisms depend on the or of locally unique sequences, sequences containing or adjacent to repeats are particularly prone to errors in replication and transcription by, or to forming problematic, and thus repeats are often unstable in the sense that the number of copies tends to expand or diminish stochastically with each round of replication, causing great even between different cells in the same organism. When repeats occur within or, these properties often result in aberrant expression and lead to disease. Repeats are also essential for normal genome function in other contexts, as with and, which consist largely of repetitive sequences.
A region or fragment of DNA consisting largely or entirely of .
See '.
1. The process by which certain biological molecules, notably the and, produce copies of themselves.
2. A technique used to estimate technical and biological variation in experiments for statistical analysis of data. Replicates may be technical replicates, such as dye swaps or repeated array, or biological replicates, biological samples from separate experiments which are used to test the effects of the same experimental treatment.
The eye-shaped structure that forms when a pair of, each growing away from the, separates the strands of the double helix during.
The point at which the paired strands of a molecule are separated by during, breaking the hydrogen bonds between the complementary strands and thereby forming a structure with two branching single strands of DNA. Once unpaired, these strands serve as from which synthesizes the and. As replication proceeds, helicase moves along the DNA and continues to separate the strands, causing the replication fork to move as well. A pair of replication forks forms when helicases work in opposite directions from a single, creating a.
The speed at which are incorporated into an elongating chain by during ; or more generally the speed at which any chromosome, genome, cell, or organism makes a complete, independently functional copy of itself.
1. Any fragment or region of DNA that contains a.
2. Any molecule or structure capable of ; namely,, but also crystals of many minerals, e.g. kaolinite.
Any molecule or region of or that from a single.
The entire complex of molecular machinery that carries out the process of, including all proteins, nucleic acids, and other molecules which participate at an active.
In, a gene which when properly expressed encodes a gene product that is easily detected or visualized with biochemical assays, allowing researchers to use its expression in order to study the functions and properties of associated. Reporters are commonly into plasmid in proximity to putative,, or, which are then mutated in order to precisely identify the specific within these sequences that are necessary for expression. In the broadest sense, reporters may also include things like molecular, fluorescent, and which render their conjugated molecules conspicuous or able to be purified; or they may be used similarly to, to distinguish cells that express a given product from those that do not, so that researchers can easily identify mutants of interest or verify the success of an experimental treatment or laboratory procedure.
See '.
A that inhibits the of one or more by binding to the and blocking the attachment of to the, thus preventing. This process is known as or.
The restoration of a defective cell or tissue to a healthy or normal condition, or the or recovery of a mutant gene to its normal functionality, especially in the context of experimental genetics, where an experiment resulting in such a restoration is said to rescue the normal.
An individual or of a larger ; e.g. a is composed of residues, and a or is composed of residues.
Any short sequence of DNA that serves some function related to the activity of a protein or other biomolecule, especially a sequence within a region that is able to bind specific in order to of specific genes.
The spontaneous rejoining of an experimentally broken which restores the original configuration.
A containing twice the expected number of chromosomes owing to an error in cell division, especially an unreduced, product of resulting from the failure of the first or second meiotic division.
The use of and the specific for them in order to molecules.
An or that recognizes and cleaves a nucleic acid molecule into at or near specific recognition sequences known as by breaking the of the nucleic acid. Restriction enzymes are naturally occurring in many organisms, but are also routinely used for artificial modification of DNA in laboratory techniques such as.
Any DNA fragment that results from the cutting of a DNA strand by a at one or more.
Variability within a population of organisms observed in the size of the produced when is by one or more. This variability results from a corresponding in the locations of restriction sites within the molecule due to slight differences in nucleotide sequence between individuals. RFLP is frequently exploited in the laboratory to construct physical, to identify the specific occupied by a particular gene, and to detect genetic differences between closely related individuals or determine that different samples originated from the same individual. Analysis of restriction fragments can also reveal the presence of a mutation that may itself cause disease or be closely linked to one that does.
A diagram of known within a known DNA sequence, such as a, obtained by systematically exposing the sequence to various and then comparing the lengths of the resulting, a technique known as. See also '.
The use of type II to cleave DNA molecules at specific in order to produce characteristic patterns of which can be resolved by size using. DNA molecules such as or with one or multiple restriction enzymes makes it possible to deduce from the sizes of the resulting fragments the order or arrangement of the restriction sites within the molecule and the distances between them, and thus to construct reliable with restriction sites effectively serving as.
A short, specific of nucleotides that is reliably recognized by a particular. Because restriction enzymes usually bind as, restriction sites are generally spanning both strands of a molecule. Restriction cleave the between two nucleotides within the recognized sequence itself, while other types of restriction enzymes make their cuts at one end of the sequence or at a nearby sequence.
A or other DNA sequence which has arisen in a genome by the stable of the genetic material of a retrovirus, e.g. by the of viral RNA and the subsequent of the resulting DNA fragments into the host cell's. These endogenous viral elements can then be replicated along with the host's own genes and thus persist indefinitely in the host genome, and in many cases retain the ability to produce functional viral proteins from this latent state, by which they may continue to copy,, and/or themselves.
An experimental approach in in which a researcher starts with a known and attempts to determine its function or its effect on phenotype by any of a variety of laboratory techniques, commonly by deliberately mutating the gene's DNA sequence or by or its and then the mutant organisms for changes in phenotype. When the gene of interest is the only one in the genome whose expression has been manipulated, any observed phenotypic changes are assumed to be influenced by it. This is the opposite of, in which a known phenotype is linked to one or more unknown genes.
An enzyme capable of synthesizing a molecule from an template, a process termed.
The synthesis of a molecule from an, i.e. the opposite of ordinary. This process, mediated by an enzyme known as a, is used by many viruses to their genomes, as well as by and in some eukaryotic cell types.
Any of a class of enzymes which catalyze the hydrolytic cleavage of in molecules, thus severing polymeric of into smaller components. Compare '.
A polymeric molecule composed of a series of which incorporate a set of four :,,, and . Unlike, RNA is more often found as a folded onto itself, rather than a paired double strand. Various types of RNA molecules serve in a wide variety of essential biological roles, including,,, and, as well as functioning as signaling molecules and, in certain viral genomes, as the primary genetic material itself.
A that is a complex of one or more molecules and one or more. Examples include and the enzyme ribonuclease P.
A containing as its pentose sugar component, and the monomeric subunit of molecules. Ribonucleotides canonically incorporate any of four :,,, and . Compare '.
An enzyme which catalyzes the formation of via the reductive dehydroxylation of, specifically by removing the 2' hydroxyl group from the ring of . RNR plays a critical role in regulating the overall rate of DNA synthesis such that the ratio of DNA to cell mass is kept constant during cell division and.
A sugar which, as D-ribose in its ring form, is one of three primary components of the from which molecules are built. Ribose differs from its structural analog only at the 2' carbon, where ribose has an attached hydroxyl group that deoxyribose lacks.
A DNA sequence that codes for . In many eukaryotic genomes, rDNA occupies large, highly conserved regions of multiple chromosomes and is rich in both and.
A type of which is the primary constituent of, binding to ribosomal proteins to form the and. It is ribosomal RNA which enables ribosomes to perform protein synthesis by working as a that catalyzes the set of reactions comprising. Ribosomal RNA is transcribed from the corresponding and is the most abundant class of RNA in most cells, bearing responsibility for the translation of all encoded proteins despite never being translated itself.
A macromolecular complex made of both RNA and protein which serves as the site of protein synthesis by. Ribosomes have two, each of which consists of one or more strands of bound to various ribosomal proteins: the, which reads the messages encoded in molecules, and the, which links in sequence to form a chain. Ribosomes are essential and ubiquitous in all cell types and are used by all known forms of life.
A sequence within a that can bind a small effector molecule, preventing or disrupting and thereby acting as a switch that regulates the mRNA's.
An molecule with enzymatic activity, i.e. one that is capable of catalyzing one or more specific biochemical reactions, similar to . Ribozymes function in numerous capacities, including in as part of the .
See '.
A that codes for any of the various types of .
Any of a class of that synthesize molecules from a template. RNA polymerases are essential for and are found in all living organisms and many viruses. They build long single-stranded polymers called by adding one at a time in the -to- direction, relying on the provided by the strand to transcribe the nucleotide sequence faithfully. Unlike, RNA polymerases notably do not require oligonucleotide to initiate synthesis; i.e. they are capable of synthesizing RNA molecules '.
A complex which works to endogenous and exogenous genes by participating in various pathways at the transcriptional and translational levels. RISC can bind both and fragments and then cleave them or use them as guides to target complementary mRNAs for degradation.
See '.
A type of by which at or near the of two cause a reciprocal exchange of segments that gives rise to one large chromosome and one extremely small chromosome, the latter of which is often subsequently lost from the cell with little effect because it contains very few genes. The resulting shows one fewer than the expected total number of chromosomes, because two previously distinct chromosomes have essentially fused together. of Robertsonian translocations are generally not associated with any phenotypic abnormalities, but do have an increased risk of generating meiotically unbalanced.
A type of membrane in the with numerous conspicuously attached to its surface, in contrast to the which lacks ribosomes. The rough ER serves as the site of protein synthesis for the majority of the cell's secreted and transmembrane proteins, as well as the site of synthesis of membrane lipids. It may be continuous with the smooth ER or exist separately.
See '.
1. An abbreviation of real-time polymerase chain reaction, synonymous with.
2. An abbreviation of.
S
The phase of the during which is, occurring after the phase and before the phase.
Any that utilizes compounds formed in for the or biosynthesis of new compounds, e.g. by recycling building block monomers such as free and to make new.
See '.
A method of based on the in vitro of a DNA sequence, during which fluorochrome-labeled, chain-terminating dideoxynucleotides are randomly incorporated in the elongating strand; the resulting fragments are then sorted by size with, and the particular fluorochrome terminating each of the size-sorted fragments is detected by laser chromatography, thus revealing the of the original DNA template through the order of the fluorochrome labels as one reads from small-sized fragments to large-sized fragments. Though Sanger sequencing has been replaced in some contexts by methods, it remains widely used for its ability to produce relatively long sequence reads and its very low error rate.
An ' nucleic acid reaction in which one polynucleotide component is supplied in great excess relative to the other, causing all complementary sequences in the other polynucleotide to pair with the excess sequences and form hybrid molecules.
See '.
A molecule or compound that is caused to accumulate in an cell by the action of a, growth factor, or other agonist and thereby brings about the action of that agonist on the cell. Second messengers are therefore critical mediators of a diverse variety of pathways, including the synthesis of by adenylate cyclase and of by guanylate cyclase, the opening of, and the of proteins by serine/threonine-specific or tyrosine-specific.
The arrangement or of a 's into higher-order, locally organized structures, primarily via hydrogen bonding between non-adjacent amino acid residues, in particular and ; or the arrangement of double-stranded chains into the shape of a stabilized by hydrogen bonds between the complementary bases.
See '.
A or other genetic material whose in cultured cells confers a selective advantage in the culture environment, causing cells expressing the gene to have one or more traits suitable for artificial selection. Selectable markers are widely used in the laboratory as a type of, usually to indicate the success of a procedure meant to introduce exogenous DNA into a host cell such as or. A common example is an which is transformed into competent bacterial cells cultured on a medium containing the particular antibiotic, such that only those cells which have successfully taken up and expressed the gene are able to survive and grow into colonies.
Any genetic material which can enhance its own and/or transmission into subsequent generations at the expense of other genes in the genome, even if doing so has no positive effect or even a net negative effect on the of the genome as a whole. Selfish elements usually work by producing self-acting which repeatedly their own into other parts of the genome, independently of normal ; by facilitating the uneven swapping of chromosome segments during events ; or by disrupting the normally equal redistribution of replicated material during or such that the probability that the selfish element is present in a given is greater than the normal 50 percent.
The standard mode of that occurs in all living cells, in which each of the two parental of the original molecule are used as, with replicating each strand separately and simultaneously in directions. The result is that each of the two double-stranded daughter molecules is composed of one of the original parental strands and one newly synthesized complementary strand, such that each daughter molecule conserves the precise sequence of information from one-half of the original molecule. Contrast ' and '.
A distinction made between the individual of a molecule in order to easily and specifically identify each strand. The two strands are distinguished as sense and antisense or, equivalently, the ' and the '. It is the antisense/template strand which is actually used as the template for ; the sense/coding strand merely resembles the sequence of on the RNA transcript, which makes it possible to determine from the DNA sequence alone the expected amino acid sequence of any protein from the RNA transcript. Which strand is which is relative only to a particular RNA transcript and not to the entire DNA molecule; that is, either strand can function as the sense/coding or antisense/template strand.
Any that specifies an, as opposed to a, which does not specify any particular amino acid but instead signals the end of translation.
See '.
In, a graphical representation of the of or at each position within a nucleic acid or protein. Sequence logos are created by many sequences and used to depict as well as the degree of within the pool of aligned sequences.
Any DNA that occurs exactly once within a particular, and whose and nucleotide sequence are known with confidence.
The determination of the order or of in a molecule, or of in a, by any means. Sequences are usually written as a linear string of letters which conveniently summarizes much of the atomic-level structure of the molecule.
See '.
The presence of a particular or DNA sequence on a rather than on an ; these genes are said to be sex-linked. Expression of sex-linked genes varies by organism depending on the mechanism of sex determination and the types of sex chromosomes present, but the associated often exclusively appear in either the homogametic or heterogametic sex.
In many prokaryotic, the, located 6–8 bases upstream of the translation, which functions as a binding site for the by complementing a sequence in the.
In condensed where the positioning of the creates two segments or "arms" of unequal length, the shorter of the two arms of a. Contrast '.
See '.
A method of in which is randomly fragmented, into vectors, and then using that anneal to flanking sequences in the plasmids. Computer software is used to via overlapping, allowing scientists to deduce the relative genomic locations of each fragment and thereby assemble a complete genome.
Any sequence of, usually 15–30 residues in length, that functions as a molecular signal directing the and transport of the bearing it to a within a cell or organelle. Signal peptides are commonly located close to either the or ends of or recently synthesized polypeptides, especially those destined for secretion from the cell or integration into a membrane, and are typically cleaved off by a dedicated when their polypeptide reaches the. Similar but distinct varieties of protein targeting are accomplished with and .
The process by which a chemical, electrical, or mechanical signal is converted into a cellular response, or the transmission or propagation of such a signal through a cell as a series of molecular events known as a. For example, the extracellular interaction of a, growth factor, or some other chemical agonist with a specific can trigger a of sequential biochemical reactions which propagate through the cell membrane and into the cytoplasm, provoking the synthesis of and leading to amplification of the signal or activation of other pathways. Other modes of transduction involve agonists which diffuse across the membrane freely, eliciting intracellular changes without amplification, or rapid shifts in which transmit electrical impulses, such as those that cause the axons of neural cells to release neurotransmitters at synapses.
A sequence or region of DNA that can be bound by a, thereby blocking the of a nearby gene.
The total or near-total loss of of a particular or DNA sequence by any mechanism, natural or artificial, whether before, during, or after or, which completely prevents the normal from being produced and thereby deprives the cell of its ordinary function. Gene silencing may occur via natural mechanisms such as condensation of the relevant segment of DNA into a transcriptionally inactive, state, in which case the term is more or less equivalent to ; genes are also commonly silenced artificially for research purposes by using techniques such as or . See also '.
An that does not produce a detectable. Compare '.
A type of which does not have an observable effect on the organism's. Though the term "silent mutation" is often used interchangeably with, synonymous mutations are not always silent, nor vice versa. which result in a different but one with similar functionality are also often classified as silent, since such mutations usually do not significantly affect protein function.
See '.
Any of a single which occurs at a specific position within a and with measurable frequency within a population; for example, at a specific base position in a DNA sequence, the majority of the individuals in a population may have a, while in a minority of individuals, the same position may be occupied by an . SNPs are usually defined with respect to a "standard" reference genome; an individual human genome differs from the reference human genome at an average of 4 to 5 million positions, most of which consist of SNPs and short. See also '.
The loss of continuity of the in one of a. See also '; contrast '.
Composed of a single, unpaired molecule, i.e. one linear of sharing a single, as opposed to a of two such strands joined by base pairing. See also ' and '.
Any molecule that consists of a single nucleotide polymer or, as opposed to a pair of complementary strands held together by hydrogen bonds. In most circumstances, DNA is more stable and more common in double-stranded form, but high temperatures, low concentrations of dissolved salts, and very high or low pH can cause double-stranded molecules to decompose into two single-stranded molecules in a process known as ; this reaction is exploited by naturally occurring enzymes such as those involved in as well as by laboratory techniques such as.
See '.
A pair of identical copies produced as the result of the of a, particularly when both copies are joined together by a common ; the pair of sister chromatids is called a dyad. The two sister chromatids are ultimately separated from each other into two different cells during or.
A class of small molecules engineered so as to change conformation conditionally in response to cognate molecular inputs, often with the goal of controlling pathways ' or '.
A class of small molecules, approximately 100–300 nucleotides in length and rich in residues, found in association with specific proteins as part of complexes known as snRNPs within and of the eukaryotic nucleus. SnRNPs assemble into larger complexes known as which play important roles in the of transcripts before they are exported to the cytoplasm.
A class of small molecules whose primary function is to direct the of other RNAs, mainly,, and especially as a part of synthesis in the. SnoRNAs contain sequences that complement sequences within these target RNAs and guide complexes to them, which can then catalyze specific nucleoside modifications, typically or.
A subclass of, originally described in nematodes, which regulate the timing of developmental events by binding to complementary sequences in the of and inhibiting their. In contrast to, which serve similar purposes, stRNAs bind to their target mRNAs after the initiation of translation and without affecting mRNA stability, which makes it possible for the target mRNAs to resume translation at a later time.
Any of a family of small, each approximately 100 amino acids, which are covalently to and removed from charged residues of other proteins in a form of known as, thereby functioning as a in a manner resembling.
A type of membrane in the that lacks on its surface, thus visibly contrasting with the. Smooth ER tends to be tubular rather than sheet-like, and may form an extension of the rough ER or exist separately. It is especially abundant in cells concerned with metabolism.
See '.
See '.
See '.
Any biological cell forming the body of an organism, or, in multicellular organisms, any cell other than a,, or undifferentiated. Somatic cells are theoretically distinct from cells of the, meaning the they have undergone can never be transmitted to the organism's descendants, though in practice exceptions do exist.
See '.
The application of sound energy at ultrasonic frequencies in order to agitate particles in a chemical or biological sample. Intense acoustic vibrations produce pressure waves and cavitations that propagate through a liquid medium, thereby converting the sound energy to mechanical energy which can disperse solutes, disrupt intermolecular interactions, and break covalent bonds. At various amplitudes sonication can be used to increase the permeability of cell or nuclear, a technique known as, or to and release their contents for isolation and extraction. It has a wide variety of applications in industry and research, including creating nanoparticles such as, shearing DNA and proteins into smaller fragments, degassing liquids, and ultrasonic cleaning.
A method used to detect a specific in samples. The method combines separation of DNA fragments by, transfer of the DNA to a synthetic membrane, and subsequent identification of target fragments with radio- or fluorescent. Compare ', ', and '.
Any sequence or region of separating neighboring, whether or not. The term is used in particular to refer to the non-coding regions between the many repeated copies of the genes. See also '.
The of one or more genes only within a specific anatomical region or tissue, often in response to a signal. The boundary between the jurisdictions of two spatially restricted genes may generate a sharp gradient there, as with striping patterns.
The structure that forms during in eukaryotic cells, consisting of a network of long, flexible extending from each pole of the and attaching to at the centromeres of or near the cell equator. As the microtubules shorten, they pull the chromosomes apart, separating them into different. Proper formation of this apparatus is critical in both and, where it is respectively referred to as the mitotic spindle and meiotic spindle.
A large complex found primarily in the nucleus of eukaryotic cells, composed of multiple small nuclear ribonucleoproteins which are themselves composed of and a variety of snRNP-specific proteins. Spliceosomes assemble at the junctions between and within and catalyze the of the introns and the of the flanking exons in a form of post-transcriptional processing known as.
Any natural or artificial process involving the of oligonucleotide sequences from nucleic acid molecules or of peptide sequences from proteins and the subsequent of the flanking fragments into a single continuous molecule lacking the excised sequence. in particular is an important form of whereby are removed from transcripts and the rejoined to create mature mRNAs; a also occurs with the removal of and the rejoining of in the of certain proteins. The term may also refer more generally to artificial techniques for creating sequences in.
See '.
See '.
See '.
The used by the vast majority of living organisms for into. In this system, of the 64 possible permutations of that can be made from the four, 61 code for one of the 20, and the remaining three code for. For example, the codon codes for the amino acid glutamine and the codon is a stop codon. The standard genetic code is described as or redundant because some amino acids can be coded for by more than one different codon.
The first by a from a mature transcript, used as a signal to initiate synthesis. In the, the start codon always codes for the same, methionine, in eukaryotes and for a modified methionine in prokaryotes. The most common start codon is the triplet. Contrast '.
A branch of genetics concerned with the development of statistical methods for drawing inferences from genetic data. The theories and methodologies of statistical genetics often support research in,, and.
Any biological cell which has not yet into a specialized cell type and which can divide through to produce more undifferentiated stem cells.
See '.
A term used to describe the end of a molecule where one is longer than the other by one or more, creating a single-stranded "overhang" of unpaired bases, in contrast to a so-called, where no such overhang exists because the terminal nucleobases on each strand are with each other. Blunt ends and sticky ends are relevant when linear DNA molecules, e.g. in, because many cleave the phosphate backbone in a way that leaves behind terminal overhangs in the digested fragments. These sticky-ended molecules ligate much more readily with other sticky-ended molecules having overhangs, allowing scientists to ensure that specific DNA fragments are ligated together in specific places.
A that signals the termination of protein synthesis during of a transcript. In the, three different stop codons are used to dissociate from the growing amino acid chain, thereby ending translation:,, and . Contrast '.
An individual chain of comprising a polymer, existing either independently or in a with another, separate strand.
The effect of conditions such as temperature and pH upon the degree of that is required for a reaction to occur between two single-stranded nucleic acid molecules. In the most stringent conditions, only exact complements can successfully hybridize; as stringency decreases, an increasing number of can be tolerated between the two hybridizing strands.
See '.
A that codes for any protein or RNA other than a. Structural gene products include,, and certain.
Any which contributes to the mechanical shape and structure of,, or, as distinguished from proteins which serve some other purpose, such as. This distinction is not well-defined, however, as many proteins have both structural and non-structural roles.
1. The subdivision of the interior of a cell into functionally distinct spaces or and the delegation of particular cellular functions and activities to these particular spaces.
2. The determination by any of various laboratory methods of the precise location within a cell where a specific molecule has occupancy, or at which a specific activity occurs.
Having a positioned close to but not exactly in the middle of the chromosome, resulting in arms of slightly different lengths. Compare '.
A type of in which a single and its attached is replaced by a different nucleotide.
1. A chemical compound or molecule upon which a particular directly acts, often but not necessarily binding the molecule by forming one or more chemical bonds. See also '.
2. The substance, biotic or abiotic, upon which an organism grows or lives, or by which it is supported; e.g. a particular used in. See also '.
A solid surface to which a cell or organism adheres or by which it is supported, or over which it moves. See also '.
A single unit of a multi-unit compound or molecular aggregate; e.g. a from which a larger is composed, or an individual chain in a multi-chain, or an entire protein which participates alongside other proteins as part of a.
A type of in which a is conjugated to a polar residue of another protein via a covalent. This effectively the second protein, making it distinguishable to other biomolecules and in many cases allowing it to participate in specific reactions or to interact with specific. SUMOlyation is closely related to, relying on the same E1/E2/E3 enzymes to transfer SUMO to specific recognition motifs in the target protein, though detaching SUMO depends on SUMO-specific. It plays important roles in numerous cellular processes, including, transcriptional regulation, stress-response pathways, and, among others. SUMOlyation is also used in the laboratory as a molecular and to help solubilize proteins which are difficult to.
See '.
A type of in which individual or aggregates of cells are suspended in a liquid, and usually prevented from settling by continuous gentle agitation. Many prokaryotic and eukaryotic cell types readily proliferate in suspension cultures, but they are particularly useful for culturing non-adherent cell lines such as hematopoietic cells, plant cells, and insect cells. Compare '.
Any of a class of which facilitate the transport of two or more different molecules across the membrane at the same time and in the same direction; e.g. glucose and sodium ions. Contrast ' and '.
A complex of scaffolding proteins that mediates and between the chromatids of homologous chromosomes during of.
A cell, i.e. a cell containing more than one or, in the broadest sense, more than one . Syncytia may form as a result of between uninucleate cells, migration of a nucleus from one cell to another, or multiple nuclear divisions without accompanying . The term may also refer to cells which are interconnected by specialized membranes with as in some neuromuscular cell types.
The of chromosomes during.
The aggregation of into a dense knot that adheres to one side of the, commonly observed during in certain organisms.
A type of in which the of one base for another results, after and, in an amino acid sequence which is identical to the original unmutated sequence. This is possible because of the of the, which allows different to code for the same amino acid. Though synonymous mutations are often considered, this is not always the case; a synonymous mutation may affect the efficiency or accuracy of,,, or any other process by which genes are, and thus become effectively non-silent. Contrast '.
See '.
T
A pattern within a in which one or more are repeated and the repetitions are directly adjacent to each other. An example is, in which the sequence is repeated three times.
The site or locus upon another molecule at which a protein performs a particular biochemical activity; e.g. the nucleotide at which a cleaves a DNA molecule, often but not necessarily the same as the enzyme's .
A highly conserved sequence containing a of repeating and base pairs that is commonly found in of genes in archaea and eukaryotes. The TATA box often serves as the site of initiation of or as a binding site for.
A directional response by a cell or a population of cells to a specific stimulus; a movement or other activity occurring in a non-random direction and dependent on the direction from which the stimulus originated. This contrasts with, a response without directional bias.
See '.
The transmission of three‐dimensional structural stability from a stable part of a macromolecule to a distal part of the same molecule, especially an inherently less stable part. Instability may also be transmitted in this way, e.g. destabilization of the DNA may occur at a that is relatively distant from the of a.
Having a positioned at the terminal end of the chromosome, resulting in only a single arm. Compare '.
A region of at each end of a linear which protects the end of the chromosome from deterioration and from fusion with other chromosomes. Since each round of results in the shortening of the chromosome, telomeres act as disposable buffers which are sacrificed to perpetual truncation instead of nearby genes; telomeres can also be lengthened by the enzyme telomerase.
The of of genes in regions adjacent to. Telomeres also appear to reduce the accessibility of subtelomeric to modification by DNA.
The final stage of cell division in both and, occurring after and before or simultaneously with, during which a nuclear membrane is synthesized around each set of, are reassembled, and the is disassembled. Following cytokinesis, the new daughter cells resume.
The of a molecule which is used as a template for RNA synthesis during. The sequence of the template strand is to the resulting RNA transcript. Contrast '; see also '.
In cytology, the progressive shift of from their original to more distal positions as proceeds through and.
See '.
A DNA or its RNA which signals the termination of by triggering processes that ultimately arrest the activity of or otherwise cause the release of the RNA from the transcriptional complex. Terminator sequences are usually found near the of the of or. They generally function after being themselves transcribed into the nascent RNA strand, whereupon the part of the strand containing the sequence either directly interacts with the transcriptional complex or forms a such as a which signals the recruitment of enzymes that promote its disassembly.
A molecular aggregate consisting of four. The term is often used to refer to composed of four proteins, e.g. haemoglobin, or to individual proteins composed of four. Compare ', ', and '.
See '.
See '.
One of the four standard used in molecules, consisting of a with its N9 nitrogen to the C1 carbon of a sugar. The prefix deoxy- is commonly omitted, since there are no ribonucleoside analogs of thymidine used in RNA, where it is replaced with instead.
A used as one of the four standard nucleobases in molecules. Thymine forms a with. In, thymine is not used at all, and is instead replaced with.
See '.
A type of specialized intercellular junction characterized by very close contact between the plasma membranes of adjacent cells, which are held together by large that completely or nearly completely occlude the passage of water and solutes through the between cells. Tight junctions occur in many vertebrate tissues, especially between the epithelial and endothelial cells that line the surfaces of most organs and vessels. These cells are completely encircled by tight junctions which create a gasket-like seal that separates each cell's plasma membrane into apical and basolateral domains and prevents the exchange of extracellular materials between them.
In a multicellular organism, a contiguous aggregation of held together by a common and specialized to perform a particular function. Some tissues are composed primarily of a single cell type; others are a heterogeneous mixture of many cell types. Tissues represent a level of multicellular organization between that of individual cells and that of organs, which may be composed of one or more distinct types of tissue.
The growth and maintenance, or "culturing", of multicellular, or of cells harvested from tissues, under carefully controlled conditions ', in the strictest sense by taking a piece of explanted tissue directly from a living plant or animal and maintaining it outside of the body of the source organism. In common usage, the term may also refer to in general, especially when growing certain cell types which have been harvested from tissues but dispersed from their original tissue-specific organization into a population of more or less independently growing cells.
Gene function and which is restricted to a particular or cell type. Tissue-specific expression is usually the result of an which is activated only in the proper cell type.
A measure of the effective osmotic pressure gradient of one solution relative to another solution, used especially to describe the water potential that exists between two aqueous solutions separated by a semipermeable membrane. Tonicity depends on the relative concentrations of solutes on either side of the membrane, which determine the direction and extent to which solvent molecules move across the membrane by ; it is affected only by those solutes which cannot cross the membrane, as those which can cross freely can achieve equilibrium without any net movement of solute. The extracellular environment is commonly described as,, or with respect to the intracellular environment.
See '.
Any of a class of enzymes which catalyze changes in the topological state of a molecule by or the of one or both strands, relaxing the torsional stress inherent in the and unwinding or untangling the paired strands before the nicks. This process is usually necessary prior to and. Topoisomerases thereby convert DNA between its and, linked and unlinked, and knotted and unknotted forms without changing the sequence or overall chemical composition, such that the substrate and product molecules are structural isomers, differing only in their shape and their,, and/or.
A state of in which a cell or nucleus fully retains the ability to into all of the represented in the adult organism, or to give rise to all of these cell types upon into an appropriate cytoplasm. Such cells or nuclei are said to be totipotent. The that serves as the progenitor cell for sexually reproducing multicellular organisms is the archetypal totipotent cell; almost all of the cells into which it ultimately differentiates are not totipotent, though some cells such as remain totipotent or throughout the organism's life.
A molecule or a specific atom within a molecule that has been chemically or radioactively so that it can be easily tracked or followed through a biochemical process or located in a cell or tissue.
See '.
On the opposite side; across from; from a different molecule. Contrast '.
Affecting a or sequence on a different nucleic acid molecule or. A or sequence within a particular DNA molecule such as a is said to be trans-acting if it or its influence or act upon other sequences located relatively far away or on an entirely different molecule or chromosome. For example, a acts "in trans" if it binds to or interacts with a sequence located on any strand or molecule different from the one on which it is encoded. Contrast '.
A form of in which different RNA, synthesized in separate events, are spliced together into a single, continuous transcript. This contrasts with the more conventional "cis-splicing", where segments of the same transcript are excised or re-arranged.
An experimental approach to artificially control by introducing a transactivator gene under the control of an inducible into a genome. The transactivator encodes a capable of upon one or more other genes by recognizing and specifically binding their promoters; thus by inducing the transactivator gene, the expression of many other genes can be experimentally manipulated.
A sequence that is transcribed and thus included in the primary but subsequently and discarded during the maturation of functional RNAs of the.
A product of ; that is, any molecule which has been synthesized by using a complementary molecule as a. When transcription is completed, transcripts separate from the DNA and become independent. Particularly in eukaryotes, multiple are usually necessary for raw transcripts to be converted into stable and persistent molecules, which are then described as mature, though not all transcribed RNAs undergo maturation. Many transcripts are accidental, spurious, incomplete, or defective; others are able to perform their functions immediately and without modification, such as certain.
Any RNA whose function is unclear. Such transcripts may include functional which have not yet been studied in detail as well as spurious transcripts without any definite function. The DNA sequences from which TUFs are transcribed are generally located in or regions of the genome. See also '.
See '.
The first step in the process of, in which an molecule, known as a, is synthesized by enzymes called using a or other sequence as a. Transcription is a critical and fundamental process in all living organisms and is necessary in order to make use of the information encoded within a. All classes of RNA must be transcribed before they can exert their effects upon a cell, though only proceeds to to produce a functional, whereas the many types of fulfill their duties without being translated. Transcription is also not always beneficial for a cell: when it occurs at the wrong time or at a, or when or infectious pathogens utilize the host's transcription machinery, the resulting transcripts are often harmful to the host cell or genome.
Any that controls the rate of of genetic information from to by binding to a specific and or the recruitment of to nearby. Transcription factors can effectively turn "on" and "off" specific genes in order to make sure they are at the right times and in the right places; for this reason, they are a fundamental and ubiquitous mechanism of.
The specific location within a at which begins, defined by the specific nucleotide or codon corresponding to the first ribonucleotide to be assembled in the transcript. This site is usually considered the beginning of the and is the reference point for numbering the individual nucleotides within a gene. Nucleotides of the start site are assigned negative numbers and those are assigned positive numbers, which are used to indicate the positions of nearby sequences or structures relative to the TSS. For example, the for RNA polymerase might be a short sequence immediately upstream of the TSS, from approximately -80 to -5, whereas an within the coding region might be defined as the sequence starting at nucleotide +207 and ending at nucleotide +793.
The segment of DNA between the and the termination site of, containing the for one or more. All genes within a transcription unit are transcribed together into a single transcript during a single transcription event; the resulting RNA may subsequently be cleaved into separate RNAs, or may be as a unit and then cleaved into separate polypeptides.
The intermittent nature of and mechanisms. Both processes occur in "bursts" or "pulses", with periods of gene activity separated by irregular intervals.
The entire set of molecules that is or can be by a particular, cell, population of cells, or species at a particular time or under particular conditions. The transcriptome is distinct from the and the.
The study of the of a particular genome, cell, or organism, i.e. the sum total of all of the RNA produced from it by. Transcriptomics technologies allow scientists to isolate and sequence transcriptomes, which can then be mapped to the genome to determine which genes are being expressed or which cellular processes are active and which are dormant at a given time.
The transport of molecules across the interior of a cell, i.e. through the, especially a such as an with contrasting and surfaces, thereby providing a spatially oriented transport system. Molecules undergoing transcytosis are usually contained within.
A cell which has undergone and been successfully transduced.
The transfer of genetic material between cells by a virus or viral vector, either naturally or artificially.
A cell which has undergone and been successfully transfected.
The deliberate experimental introduction of exogenous into a cell or embryo. In the broadest sense the term may refer to any such transfer and is sometimes used interchangeably with, though some applications restrict the usage of transfection to the introduction of naked or purified non-viral or into cultured eukaryotic cells resulting in the subsequent incorporation of the foreign DNA into the host or the non-hereditary modification of by the foreign RNA. As a contrast to both standard non-viral transformation and, transfection has also occasionally been used to refer to the uptake of purified viral nucleic acids by bacteria or plant cells without the aid of a viral vector.
A special class of molecule, typically 76 to 90 in length, that serves as a physical adapter allowing transcripts to be into sequences of during protein synthesis. Each tRNA contains a specific triplet corresponding to an amino acid that is covalently attached to the tRNA's opposite end; as translation proceeds, tRNAs are recruited to the, where each mRNA is paired with a tRNA containing the complementary anticodon. Depending on the organism, cells may employ as many as 41 distinct tRNAs with unique anticodons; because of within the, several tRNAs containing different anticodons carry the same amino acid.
Any of a class of which the chemical transfer of a functional group or substituent from one molecule to another. For example, acetyltransferases catalyze the movement of an acetyl group in a process known as ; methyltransferases catalyze the movement of one or more methyl groups in a process known as.
A type of RNA molecule in some bacteria which has dual -like and -like properties, allowing it to simultaneously perform a number of different functions during.
A cell or organism which has taken up extracellular DNA by and which can express genes encoded by it.
Any or other segment of genetic material that has been isolated from one organism and then transferred either naturally or by any of a variety of techniques into another organism, especially one of a different species. Transgenes are usually introduced into the second organism's. They are commonly used to study gene function or to confer an advantage not otherwise available in the unaltered organism.
A in which a nucleotide is substituted for another purine or a nucleotide is substituted for another pyrimidine. Contrast '.
The second step in the process of, in which the transcript produced during is read by a to produce a functional.
The entire set of molecules that are by a particular, cell, tissue, or species at a particular time or under particular conditions. Like the, it is often used as a proxy for quantifying levels of, though the transcriptome also includes many RNA molecules that are never translated.
A type of chromosomal abnormality caused by the structural rearrangement of large sections of one or more. There are two main types: and.
See '.
The branch of genetics that studies the mechanisms involved in the transfer of genes from parents to offspring.
Any which functions by permitting the movement of particular molecules, proteins, or other substances across a, either or and in either or both directions. and are examples of transport proteins.
See '.
Any of a diverse variety of consisting of self-acting DNA sequences capable of themselves semi-autonomously and into random or specific sites within a host genome, a process known as. Transposons contain one or more genes which encode enzymes known as capable of recognizing sequences within a flanking pair of, such that the enzymes effectively catalyze their own replication,, and/or re-insertion into other DNA molecules by any of various mechanisms.
Any of a class of self-acting capable of to the flanking sequences of the which encodes them and catalyzing its movement to another part of the genome, typically by an / mechanism or a replicative mechanism, in a process known as.
The process by which a nucleic acid sequence known as a changes its position within a, either by and re-inserting itself at a different or by itself and inserting into another locus without moving the original element from its original locus. These reactions are catalyzed by an enzyme known as a which is encoded by a gene within the transposable element itself; thus the element's products are self-acting and can autonomously direct their own replication. Transposed sequences may re-insert at random loci or at sequence-specific targets, either on the same DNA molecule or on different molecules.
A in which a nucleotide is substituted for a nucleotide, or vice versa. Contrast '.
See '.
Any of a class of chemical compounds which are ester derivatives of glycerol, consisting of a glycerol backbone connected to any three substituents via ester bonds. Triglycerides are one of three major classes of esters formed by fatty acids in biological systems, along with and cholesteryl esters. They are the primary constituent of tissue in vertebrates.
A molecular aggregate consisting of three. The term is often used to refer to composed of three proteins, e.g. many membrane porins, or to individual proteins composed of three. Compare ', ', and '.
Any sequence in which an individual nucleotide is many times, whether in a gene or non-coding sequence. At most some degree of repetition is normal and harmless, but mutations which cause specific triplets to increase in above the normal range are highly unstable and responsible for a variety of.
A unit of three successive in a or molecule. A triplet within a coding sequence that codes for a specific amino acid is known as a.
A type of in which a cell or organism has three copies of a particular instead of the normal two.
See '.
See '.
The directional growth or movement of a cell or organism in response to a stimulus, e.g. light, heat, the pull of gravity, or the presence of a particular chemical, such that the response is dependent on the direction of the stimulus. Positive tropism is growth or movement toward the stimulus; negative tropism is away from the stimulus. See also ' and '.
The force within a cell which pushes the against the, a type of hydrostatic pressure influenced by the of water into and out of the cell. Turgidity is observed in plants, fungi, bacteria, and some protists with cell walls, but generally not in animal cells.
In, a measure of the rate at which a particular a particular biochemical reaction, usually expressed as the average number of molecules it is capable of converting into reaction products per unit time at a given concentration of enzyme.
U
A small of 76 amino acids found in great quantities in all eukaryotic cells, employed chiefly as a, by which its C-terminal glycine residue is covalently bonded to electrically charged within other proteins or polypeptides, a process known as. Ubiquitin tags have functions in the,,,,, regulation of the,, and, among others.
The of a biomolecule by covalently attaching a protein to it—generally via the formation of an amide bond between the ubiquitin's C-terminal glycine and positively charged side chains of the labelled molecule, an -dependent reaction catalyzed by ubiquitin-conjugating enzymes—thus making it identifiable to molecules capable of recognizing ubiquitin. Ubiquitination is a widely used by which proteins are ; the attachment of a single ubiquitin molecule can variously activate or inhibit a protein's activity, while the attachment of a chain of multiple consecutively linked ubiquitin molecules commonly targets the protein for degradation by.
See '.
A without an attached. Contrast '.
See '.
A type of which catalyzes the movement of a single, specific solute or chemical species across a lipid membrane in either direction. Contrast ' and '.
A class of DNA determined by to be present only once in the analyzed genome, as opposed to. Most structural genes and their introns are unique.
A with a high frequency of.
Any sequence which is transcribed along with a, and thus included within a, but which is not ultimately during protein synthesis. A typical mRNA transcript includes two such regions: one immediately upstream of the coding sequence, known as the, and one downstream of the coding sequence, known as the . These regions are not removed during and are usually considered distinct from the and the . UTRs are a consequence of the fact that transcription usually begins considerably upstream of the of the coding sequence and terminates long after the has been transcribed, whereas translation is more precise. They often include motifs with regulatory functions.
Any process, natural or artificial, which increases the level of of a certain. A gene which is observed to be expressed at relatively high levels in one sample compared to another sample is said to be upregulated. Contrast '.
Towards or closer to the of a chain of, or the of a chain. Contrast .
A type of found in the DNA of yeast such as Saccharomyces cerevisiae, usually a few hundred base pairs upstream of the within the of a protein-coding gene, which helps to increase the gene's expression by serving as a binding site for transcriptional, analogous to the function of an in multicellular eukaryotes.
A used as one of the four standard nucleobases in molecules. Uracil forms a with. In, uracil is not used at all, and is instead replaced with.
One of the four standard used in molecules, consisting of a with its N9 nitrogen to the C1 carbon of a sugar. In, uridine is replaced with.
V
Any of a class of, fluid-filled present in many eukaryotic cells as well as bacteria, often large and conspicuous under the microscope and serving any of a huge variety of functions, including acting as a resizable reservoir for the storage of water,, toxins, or foreign material; maintaining cellular and ; supporting immune functions; housing symbiotic bacteria; and assisting in the of old cellular components.
Any of a class of for which the of the at a particular locus tends to vary between individuals of the same species. VNTRs may occur throughout the genome, both within and outside of, and if the copy number is stably inherited may be used in to uniquely identify individuals or to determine their genealogical relatedness to other individuals.
Variation or irregularity in a particular, especially a conspicuous visible such as color or pigmentation, occurring simultaneously in different parts of the same individual organism due to any of a variety of causes, such as,, activity,, or infection by pathogens.
Any molecule used as a vehicle to artificially transport foreign genetic material into another cell, where it can be and/or. Vectors are typically engineered sequences consisting of an and a longer "backbone" sequence containing an, a, and a. Vectors are widely used in molecular biology laboratories to isolate,, or the insert in the target cell.
See .
Any space completely enclosed by its own, which is separate though usually derived from other membranes either by or by mechanical disruption such as. The term is applied to many different structures but especially to the small, roughly spherical created during and, as well as to and various other small intracellular or extracellular organelles.
W
A method used for detecting and identifying specific in heterogeneous biological samples. The technique involves separating proteins by size with and then immobilizing them upon a nitrocellulose, nylon, or other synthetic membrane, after which they may be visualized by autoradiography or by with chemiluminescent, radioactive, or,, or other specific binding agents. Compare ', ', and .
The process of the entirety or near-entirety of the DNA sequences comprising an organism's with a single procedure or experiment, generally inclusive of all and DNA.
The of the typical form of a species as it occurs in nature; a product of the standard "normal" at a given, as opposed to that produced by a non-standard allele.
An index of the of a DNA molecule. The writhing number does not have a precise quantitative definition but instead represents the degree of supercoiling. Together, the writhing number and the determine the.
X
One of two present in organisms which use the XY sex-determination system, and the only sex chromosome in the X0 system. The X chromosome is found in both males and females and typically contains much more content than its counterpart, the.
The process by which one of the two copies of the is silenced by being irreversibly condensed into transcriptionally inactive in the cells of female therian mammals. A form of, X-inactivation prevents females from producing twice as many from genes on the X chromosome as males, who only have one copy of the X chromosome. Which X chromosome is inactivated is randomly determined in the early embryo, making it possible for cell lineages with different inactive Xs to exist in the same organism.
A whose expression is governed or influenced by one or more genes located on the .
Y
One of two present in organisms which use the XY sex-determination system. The Y chromosome is found only in males and is typically much smaller than its counterpart, the.
See .
Z
A structural motif and occurring in many, characterized by a series of non-adjacent amino acid which into a three-dimensional arrangement capable of coordinating one or more zinc ions between them, thus stabilizing the fold into a definite structure that can interact specifically with other biomolecules such as nucleic acids or other polypeptides. There are many distinct classes of zinc fingers using different ligands and spatial arrangements to achieve coordination; in perhaps the most common variant, a short is oriented antiparallel to a, with two histidine residues in the former and two cysteines in the latter forming the coordination complex. Zinc fingers bind DNA as the primary functional domain of many.
See '.
See '.
In, the second of five substages of, following and preceding. During zygonema, occurs, physically binding to each other, and the cell's divides into two daughter centrosomes, each containing a single.
The degree to which multiple copies of a,, or have the same genetic sequence; e.g. in a diploid organism with two complete copies of its genome, the degree of similarity of the present in each copy. Individuals carrying two different alleles for a particular gene are said to be ' for that gene; individuals carrying two identical alleles are said to be ' for that gene. Zygosity may also be considered collectively for a group of genes, or for the entire set of genes and genetic comprising the genome.
A type of eukaryotic cell formed as the direct result of a fertilization event between two. In multicellular organisms, the zygote is the earliest developmental stage.