Tetrasomy

A Tetrasomy is a kind of aneuploidy that implicates an extra chromosome pair as a result of the presence of four copies of a specific chromosome, in an otherwise diploid cell. (Tetrasomic Chromosome Formula 2N + 2) ^[1][2].

Tetrasomy occurs due to nondisjunction in meiosis when both parents produce a gamete each that presents two copies of an individual chromosome, while all other chromosomes in the set present only one copy. The result is a fetus that contains 48 chromosomes, instead of the common 46 chromosomes ^[3].

Examples of tetrasomies abnormalities for autosomes and for sex chromosomes found in humans:

Sex-chromosome tetrasomies: ^[4]

• 48, XXYY and 48, XXXY: variations of the Klinefelter syndrome (occur in 1 in 18,000–50,000 male births) ^[5].
• 48, XXXX syndrome

Autosomal tetrasomies^[6]

• Cat eye syndrome
• Pallister-Killian syndrome (tetrasomy 12p)
• Tetrasomy 18p
• Tetrasomy 9p
  

References

1. ↑ http://ghr.nlm.nih.gov/glossary=tetrasomy
2. ↑ Genetics, Rusell (Fifth Edition), Peter J. Rusell). P (207-209)
3. ↑ Genetics, Rusell (Fifth Edition), Peter J. Rusell). P (207-209)
4. ↑ https://en.wikipedia.org/wiki/Tetrasomy
5. ↑ https://en.wikipedia.org/wiki/Klinefelter_syndrome
6. ↑ https://en.wikipedia.org/wiki/Tetrasomy