A premutation is a situation in which there are an excess number of repeats in a gene that is at risk of increasing in length during reproduction but which does not cause disease in the person with the excess number of repeats. Fragile X syndrome, a trinucleotide repeat disorder, is a condition in which premutations may be present in the parents of affected people. Huntington's disease is another example of a trinucleotide repeat disorder in which individuals with a certain excess of repeats (27–39) of the CAG codon in the Huntingtin gene may not have the disease but are more likely to have a child with enough repeats (40+) to cause the disease.
References
- Gersen, Steven L.; Keagle, Martha B. (2008). The Principles of Clinical Cytogenetics. Springer Science & Business Media. p. 505. ISBN 9781592598335.
- "fragile X syndrome". Genetics Home Reference. April 2012. Archived from the original on 9 October 2016. Retrieved 7 October 2016.
- Walker FO (January 2007). "Huntington's disease". Lancet. 369 (9557): 218–28. doi:10.1016/S0140-6736(07)60111-1. PMID 17240289. S2CID 46151626.