Tetrasomy
A tetrasomy is a form of aneuploidy with the presence of four copies, instead of the normal two, of a particular chromosome.
Causes
Full
Full tetrasomy of an individual occurs due to non-disjunction when the cells are dividing to form egg and sperm cells. This can result in extra chromosomes in a sperm or egg cell. After fertilization, the resulting fetus has 48 chromosomes instead of the typical 46.Autosomal tetrasomies
- Cat eye syndrome where partial tetrasomy of chromosome 22 is present
- Pallister-Killian syndrome
- Tetrasomy 9p
- Tetrasomy 18p
- Tetrasomy 21, a rare form of Down syndrome
Sex-chromosome tetrasomies
- Tetrasomy X
- XXYY syndrome
- XXXY syndrome