Tetrasomy

Tetrasomy
Classification and external resources
Specialty	medical genetics
ICD-10	Q97 - Q98
MeSH	D000782
Orphanet	3305
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A tetrasomy is a form of aneuploidy with the presence of four copies, instead of the normal two, of a particular chromosome.

Full tetrasomy of an individual occurs due to non-disjunction when the cells are dividing (meiosis I or II) to form egg and sperm cells (gametogenesis). 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.