premutation

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.{{cite book |last1=Gersen |first1=Steven L. |last2=Keagle |first2=Martha B. |title=The Principles of Clinical Cytogenetics |date=2008 |publisher=Springer Science & Business Media |isbn=9781592598335 |page=505 |url=https://books.google.com/books?id=hSDrd9MfSCEC&pg=PA505 |language=en}} Fragile X syndrome, a trinucleotide repeat disorder, is a condition in which premutations may be present in the parents of affected people.{{cite web|url=https://ghr.nlm.nih.gov/condition/fragile-x-syndrome|title=fragile X syndrome|date=April 2012|website=Genetics Home Reference|archiveurl=https://web.archive.org/web/20161009162713/https://ghr.nlm.nih.gov/condition/fragile-x-syndrome|archivedate=9 October 2016|url-status=live|accessdate=7 October 2016}} 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.{{cite journal|vauthors=Walker FO|date=January 2007|title=Huntington's disease|journal=Lancet|volume=369|issue=9557|pages=218–28|doi=10.1016/S0140-6736(07)60111-1|pmid=17240289|s2cid=46151626}}

References

Category:Mutation