DNA-Triplet Repeats and Neurologic Disease

Abstract
Beginning in 1991, our understanding of the molecular bases of nine important neurologic diseases has burgeoned. A new class of molecular disease has been identified, defined by the abnormal, unstable expansion of DNA-triplet repeats in the mutant, causal gene for each of these disorders. In this issue of the Journal, Dürr et al.1 report on a large series of patients with the triplet DNA expansion that causes Friedreich's ataxia. This report should be understood in the context of the molecular genetics of this group of neurologic diseases.The first triplet disease described was the fragile X syndrome, which has been . . .