Trinucleotide repeat expansions in neurological disease.

During the past year, new examples of human neurological disease have been discovered that have an unprecedented type of mutation as their cause: the remarkable expansion of trinucleotide repeats. These triplet repeats are normally polymorphic and exonic, though not always coding. In disease states they become markedly unstable and may expand moderately or by thousands of repeats in a single generation, influencing gene expression, message stability or protein structure.