Triplet Repeat ExpansionsComments
parentGenetic disease
siblingsAndrogen InsensitivityBalanced RearrangementCancer geneticsChromosome Number AbnormalitiesCystic FibrosisDown SyndromeDuchenne Muscular DystrophyFragile X SyndromeHemoglobinopathyHuntington DiseaseHurler SyndromeHyperphenylalaninemiamRNA Splicing AberrationsNondisjunctionPenis-At-Twelve SyndromeRelative RiskSickle Cell DiseaseSpinal Muscular AtrophyTay-Sachs DiseaseThalassemiaTrisomy 13Trisomy 18Unbalanced RearrangementUniparental Disomy

Triplet Repeat Expansions

There are numerous diseases which arise from expansions in (CAG)n repeats, which encode glutamine. In a coding region, a (CAG)n repeat expansion can either inactivate a protein or exhibit a dominant phenotype due to poly-glutamine's toxic effects; examples include Huntington Disease and Spinocerebellar Ataxia (SCA) type I. In a non-coding region, a (CAG)n repeat expansion can interfere with chromatin structure and disrupt transcriptional regulation, and/or exhibit a dominant phenotype by distracting splicing factors with the triplet repeat; examples include Myotonic Dystrophy, Fragile X Syndrome and other SCA forms.