Tetrasomy
A tetrasomy is a form of aneuploidy with the presence of four copies, instead of the normal two, of a particular chromosome.
| Tetrasomy | |
|---|---|
| Specialty | Medical genetics |
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
- 48, XXXX syndrome
- 48, XXYY syndrome
- Klinefelter's syndrome, where XXY tetrasomy is present
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