Dictionary of Human Evolution and Biology

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Huntington Disease

Inherited condition characterized by progressive degeneration of the nervous system and premature death; onset generally occurs at middle age, but age of onset decreases with each generation. HD is caused by a mutation in an autosomal dominant gene (HD) that codes for the huntingtin protein (HTT). The defect consists of up to 85 expansion repeats or stutters of the nucleotide sequence CAG in the first exon. The resulting mutant protein, mHTT, apparently folds differently than native HTT, is cleaved, and then migrates abnormally into the cell nucleus. Five per cent of the population of the villagers of Maracaibo, Venezuela, have HD due to founder effect and genetic drift. HD exhibits evidence for anticipation of a trinucleotide repeat, for genomic imprinting, and for a parent-of-origin effect; the symptoms appear in adolescence and are more severe if inherited from the father, less severe and occur in middle age if inherited from the mother. Aka chorea St. Vitus, Huntington’s chorea, Woody Guthrie disease.

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