triplet repeat expansion mutation causes a nucleotide repeat disorder like fragile x syndrome.
triplet repeat expansion mutation causes a nucleotide repeat disorder like fragile x syndrome.
what type of mutation causes a nucleotide repeat disorder like fragile x syndrome?
triplet repeat expansion
trinucleotide repeat expansion, also known as triplet repeat expansion, is the dna mutation responsible for causing any type of disorder categorized as a trinucleotide repeat disorder. these are labelled in dynamical genetics as dynamic mutations.
trinucleotide repeat disorder
since the early 1990s, a new class of molecular disease has been characterized based upon the presence of unstable and abnormal expansions of dna-triplets (trinucleotides). the first triplet disease to be identified was fragile x syndrome, which has since been mapped to the long arm of the x chromosome. at this point, there are from 230 to 4000 cgg repeats in the gene that causes fragile x syndrome in these patients, as compared with 60 to 230 repeats in carriers and 5 to 54 repeats in unaffected individuals. the chromosomal instability resulting from this trinucleotide expansion presents clinically as intellectual disability, distinctive facial features, and macroorchidism in males. the second, related dna-triplet repeat disease, fragile x-e syndrome, was also identified on the x chromosome, but was found to be the result of an expanded ccg repeat. identifying trinucleotide repeats as the basis of disease has brought clarity to our understanding of a complex set of inherited neurological diseases.
trinucleotide repeat disorder