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Genetic and Rare Diseases Information Center (GARD)

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Mosaic trisomy 14

Other Names for this Disease
  • Mosaic trisomy chromosome 14
  • Trisomy 14 mosaicism
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What causes mosaic trisomy 14?

Individuals with mosaic trisomy 14 have a duplication of chromosome 14 material in some of their cells, while other cells have a normal chromosomal makeup. The additional chromosomal material is responsible for the features that are characteristic of the condition.[1]

Most cases of mosaic trisomy 14 appear to result from random errors in the separation of chromosomes (nondisjunction) -- either during the division of the egg or sperm in one of the parents, or during cell division after fertilization. There have been some reports in which it may have occurred due to other phenomenon, such as uniparental disomy or the formation of an isochromosome. Uniparental disomy is when an affected individual inherits both copies of a chromosomal pair from one parent, rather than one copy from each parent. An isochromosome is an abnormal chromosome with identical arms on each side of the centromere.[1]

Unique has a leaflet on their Web site that contains additional descriptions and illustrations of how mosaic trisomy 14 may occur. Click here to view the leaflet.
Last updated: 11/16/2012

  1. Chromosome 14, Trisomy Mosaic. NORD. May 26, 2008; Accessed 11/13/2012.
  2. Trisomy 14 mosaicism. Unique. 2008; Accessed 11/14/2012.