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February 3, 1993

A Novel, Unstable DNA Mutation Cracks Decades-Old Clinical Enigma

JAMA. 1993;269(5):557-558. doi:10.1001/jama.1993.03500050015003

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AS GENETICISTS have located the mutations that cause one disease after another in recent years, the novelty of such discoveries has perhaps worn thin. As expected, most of the mutations have fit comfortably within the paradigm of classical genetics. Without diminishing the importance of these achievements, observers draw the parallel that even a moon landing loses its luster after several successes.

It is remarkable then, that a newly discovered mutation can rock the genetics community as it did recently at the annual meeting of the American Society of Human Genetics in San Francisco, Calif.

Causing such excitement were not only the diseases that share this mutation—fragile X syndrome, myotonic dystrophy, and Kennedy disease—but the mutation itself, which is completely novel and, until it was sequenced, beyond the imagination of geneticists. It is neither an insertion, deletion, or point mutation, and its discovery is as surprising as expecting moon rocks and