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Science 8 March 1996:
Vol. 271. no. 5254, p. 1341
DOI:

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In certain diseases, regions of repeated nucleotide triplets (either CGC or CAG) that normally contain 20 to 30 repeats expand unstably to hundreds or thousands of repeats and interfere with normal gene expression. These diseases have shown dominant inheritance and exhibit genetic anticipation (the number of repeats increases with each generation, and the severity of symptoms increases with succeeding generations). Friedreich's ataxia (FRDA), an autosomal recessive degenerative disease of the peripheral nervous system and heart that often strikes in adolescence, would not be a strong triplet repeat candidate, but Campuzano et al. (p. 1423; see the Perspective by Warren, p. 1374) have identified an expanded GAA repeat associated with the chi25 gene. Most of the FRDA patients had an unstable GAA repeat in the first intron of the gene that reduced the RNA expression of its product, frataxin.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)