Gregor Mendel
Gregor Johann Mendel OSA was an Austrian biologist, meteorologist, mathematician, Augustinian friar and abbot of St. Thomas' Abbey in Brno, Margraviate of Moravia. Mendel was born in a German-speaking family in the Silesian part of the Austrian Empire and gained posthumous recognition as the founder of the modern science of genetics. Though farmers had known for millennia that crossbreeding of animals and plants could favor certain desirable traits, Mendel's pea plant experiments conducted between 1856 and 1863 established many of the rules of heredity, now referred to as the laws of Mendelian inheritance.
Mendel worked with seven characteristics of pea plants: plant height, pod shape and color, seed shape and color, and flower position and color. Taking seed color as an example, Mendel showed that when a true-breeding yellow pea and a true-breeding green pea were cross-bred, their offspring always produced yellow seeds. However, in the next generation, the green peas reappeared at a ratio of 1 green to 3 yellow. To explain this phenomenon, Mendel coined the terms "recessive" and "dominant" in reference to certain traits. In the preceding example, the green trait, which seems to have vanished in the first filial generation, is recessive, and the yellow is dominant. He published his work in 1866, demonstrating the actions of invisible "factors"—now called genes—in predictably determining the traits of an organism. The actual genes were only discovered in a long process that ended in 2025 when the last three of the seven Mendel genes were identified in the pea genome.
The profound significance of Mendel's work was not recognized until the turn of the 20th century with the rediscovery of his laws. Erich von Tschermak, Hugo de Vries and Carl Correns independently verified several of Mendel's experimental findings in 1900, ushering in the modern age of genetics.
Early life and education
Mendel was born into a German-speaking family in Heinzendorf bei Odrau, in Silesia, Austrian Empire. He was the son of Anton and Rosine Mendel and had one older sister, Veronika, and one younger, Theresia. They lived and worked on a farm which had been owned by the Mendel family for at least 130 years. During his childhood, Mendel worked as a gardener and studied beekeeping. As a young man, he attended gymnasium in Troppau. Due to illness, he had to take four months off during his gymnasium studies. From 1840 to 1843, he studied practical and theoretical philosophy and physics at the Philosophical Institute of the University of Olomouc, taking another year off because of illness. He also struggled financially to pay for his studies, and Theresia gave him her dowry. Later he helped support her three sons, two of whom became doctors.He became a monk partly because it enabled him to obtain an education without paying for it himself. As the son of a struggling farmer, the monastic life, in his words, spared him the "perpetual anxiety about a means of livelihood." Born Johann Mendel, he was given the name "Gregor" when he joined the Order of Saint Augustine.
Academic career
When Mendel entered the Faculty of Philosophy, the Department of Natural History and Agriculture was headed by Johann Karl Nestler, who conducted extensive research on hereditary traits of plants and animals, especially sheep. Upon recommendation of his physics teacher Friedrich Franz, Mendel entered the Augustinian St Thomas's Abbey in Brno and began his training as a Catholic priest. Mendel worked as a substitute high school teacher. In 1850, he failed his exams' oral part, the last of three parts, to become a certified high school teacher. In 1851, he was sent to the University of Vienna to study under the sponsorship of Abbot Cyril František Napp so that he could get a more formal education. At Vienna, his professor of physics was Christian Doppler. Mendel returned to his abbey in 1853 as a teacher, principally of physics. In 1854 he met Aleksander Zawadzki who encouraged his research in Brno. In 1856, he took the exam to become a certified teacher and again failed the oral part. In the summer of 1862, he joined an organised group tour to Paris and London, where he visited the International Exhibition and major scientific sites, a trip that may have influenced the final stage of his hybridisation research. In 1867, he succeeded Napp as abbot of the monastery.After he was elevated as abbot in 1868, his scientific work largely ended, as Mendel became overburdened with administrative responsibilities, especially a dispute with the civil government over its attempt to impose special taxes on religious institutions. Mendel died on 6 January 1884, at the age of 61, in Brno, from chronic nephritis. Czech composer Leoš Janáček played the organ at his funeral. After his death, the succeeding abbot burned all papers in Mendel's collection, to mark an end to the disputes over taxation. The exhumation of Mendel's corpse in 2021 delivered some physiognomic details like body height. His genome was analysed, revealing that Mendel was predisposed to heart problems.
Contributions
Experiments on plant hybridization
Mendel, known as the "father of modern genetics," chose to study variation in plants in his monastery's experimental garden. Mendel was assisted in his experimental design by Aleksander Zawadzki while his superior abbot Napp wrote to discourage him, saying that the Bishop giggled when informed of the detailed genealogies of peas.After initial experiments with pea plants, Mendel settled on studying seven traits that seemed to be inherited independently of other traits: seed shape, flower color, seed coat tint, pod shape, unripe pod color, flower location, and plant height. He first focused on seed shape, which was either angular or round. Between 1856 and 1863 Mendel cultivated and tested some 28,000 plants, the majority of which were pea plants. This study showed that, when true-breeding different varieties were crossed to each other, in the second generation, one in four pea plants had purebred recessive traits, two out of four were hybrids, and one out of four were purebred dominant. His experiments led him to make two generalizations, the Law of Segregation and the Law of Independent Assortment, which later came to be known as Mendel's Laws of Inheritance.
Initial reception of Mendel's work
Mendel presented his paper, Versuche über Pflanzenhybriden, at two meetings of the Natural History Society of Brno in Moravia on 8 February and 8 March 1865. It generated a few favorable reports in local newspapers, but was ignored by the scientific community. When Mendel's paper was published in 1866 in Proceedings of the Natural History Society of Brünn, it was seen as essentially about hybridization rather than inheritance, had little impact, and was cited only about three times over the next thirty-five years. His paper was criticized then but is now considered a seminal work. Notably, Charles Darwin was not aware of Mendel's paper, and it is envisaged that if he had been aware of it, genetics as it exists now might have taken hold much earlier. Mendel's scientific biography thus provides an example of the failure of obscure, highly original innovators to receive the attention they deserve.Rediscovery of Mendel's work
About forty scientists listened to Mendel's two groundbreaking lectures, but it would appear that they failed to understand the implications of his work. Later, he also carried on a correspondence with Carl Nägeli, one of the leading biologists of the time, but Nägeli also failed to appreciate Mendel's discoveries. At times, Mendel must have entertained doubts about his work, but not always: "My time will come," he reportedly told a friend, Gustav von Niessl.During Mendel's lifetime, most biologists held the idea that all characteristics were passed to the next generation through blending inheritance, in which the traits from each parent are averaged. Instances of this phenomenon are now explained by the action of multiple genes with quantitative effects. Charles Darwin tried unsuccessfully to explain inheritance through a theory of pangenesis. It was not until the early 20th century that the importance of Mendel's ideas was realized.
By 1900, research aimed at finding a successful theory of discontinuous inheritance rather than blending inheritance led to independent duplication of his work by Hugo de Vries and Carl Correns and the rediscovery of Mendel's writings and laws. Both acknowledged Mendel's priority, and it is thought probable that de Vries did not understand the results he had found until after reading Mendel. Though Erich von Tschermak was originally also credited with rediscovery, this is no longer accepted because he did not understand Mendel's laws. Though de Vries later lost interest in Mendelism, other biologists started to establish modern genetics as a science. All three of these researchers, each from a different country, published their rediscovery of Mendel's work within a two-month span in the spring of 1900.
Mendel's results were quickly replicated, and genetic linkage quickly worked out. Biologists flocked to the theory; even though it was not yet applicable to many phenomena, it sought to give a genotypic understanding of heredity, which they felt was lacking in previous studies of heredity, which had focused on phenotypic approaches. Most prominent of these previous approaches was the biometric school of Karl Pearson and W. F. R. Weldon, which was based heavily on statistical studies of phenotype variation. The strongest opposition to this school came from William Bateson, who perhaps did the most in the early days of publicising the benefits of Mendel's theory. This debate between the biometricians and the Mendelians was extremely vigorous in the first two decades of the 20th century, with the biometricians claiming statistical and mathematical rigor, whereas the Mendelians claimed a better understanding of biology. Modern genetics shows that Mendelian heredity is, in fact, an inherently biological process, though not all genes of Mendel's experiments are yet understood.
Ultimately, the two approaches were combined, especially by work conducted by R. A. Fisher as early as 1918. The combination, in the 1930s and 1940s, of Mendelian genetics with Darwin's theory of natural selection resulted in the modern synthesis of evolutionary biology.
In the Soviet Union and the People's Republic of China, Mendelian genetics was rejected in favor of Lamarckism under the state policy of Lysenkoism, leading to imprisonment and even execution of Mendelian geneticists as well as massive famines in both of those countries.