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 (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.
Autosomal tetrasomies
Cat eye syndrome where partial tetrasomy of chromosome 22 is present Pallister-Killian syndrome (tetrasomy 12p) Tetrasomy 9p Tetrasomy 18p Tetrasomy 21, a rare form of Down syndrome
Sex-chromosome tetrasomies
Tetrasomy X XXYY syndrome XXXY syndrome
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