Unformatted text preview: The name of the syndrome was changed to the fragile X syndrome . The puzzling genetics remained unclear. Eventually the mutation was tracked down to a trinucleotide expansion in the gene now named FMR1 (Fragile site with Mental Retardation) at the site of the secondary constriction. As in the case of myotonic dystrophy symptomless premutations could occur (and were the cause of the transmitting males). Only when the premutation chromosomes were transmitted through females did expansion to the full mutant allele and phenotype occur. A number of diseases have now been ascribed to trinucleotide expansions. These include Huntington's disease ....
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- Fall '10
- Chemistry, Mental retardation, Fragile X syndrome, Martin-Bell Syndrome, secondary constriction, commonest inherited cause