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Genetic and Rare Diseases Information Center (GARD)

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Chromosome 20 trisomy

Other Names for this Disease
  • Mosaic trisomy 20
  • Trisomy 20
  • Trisomy 20 mosaicism
  • Trisomy chromosome 20
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How is chromosome 20, trisomy inherited?

Most cases of chromosome 20, trisomy are not inherited and result from random events during the formation of eggs and sperm in healthy parents. An error in cell division, called nondisjunction, results in an egg or sperm cell with an abnormal number of chromosomes. If an egg or sperm cell gains an extra copy of chromosome 20, the embryo will have an extra chromosome 20 in each cell of the body. For more information about the causes of different types of chromosome 20, trisomy (full, partial or mosaic trisomy 20) click here.

Translocation trisomy 20 can be inherited. A  healthy person (that does not have trisomy 20) can carry a rearrangement of genetic material between chromosome 20 and another chromosome (called a translocation). These rearrangements are called balanced translocations because there is no extra material from chromosome 20. A person with a balanced translocation involving chromosome 20 has an increased chance of passing extra material from chromosome 20 to his/her child, which would result in a form of trisomy 20 in the child.[1]
Last updated: 12/17/2010

  1. Trisomy 13. Genetics Home Reference. January, 2009; Accessed 12/17/2010.