FMR1 TRIPLET ARRAYS - PAYING THE PRICE FOR PERFECTION

Our understanding of FMR1 trinucleotide instability has increased dram atically with knowledge of its detailed structures. While most arrays seem to be protected by interspersions, for a few the price of perfect ion is instability. Although there remain many unanswered questions, d iagnosis in the ''grey zone'' can be greatly improved by studying arra y content. For the future, as we strive to delineate normal from premu tation, we should increasingly be able to estimate rates of instabilit y for future generations and predict the risk of conversion to the ful l mutation.