Abstract

Our understanding of FMRI trinucleotide instability has increased dramatically with knowledge of its detailed structures. While most arrays seem to be protected by interspersions, for a few the price of perfection is instability. Although there remain many unanswered questions, diagnosis in the “grey zone” can be greatly improved by studying array content. For the future, as we strive to delineate normal from premutation, we should increasingly be able to estimate rates of instability for future generations and predict the risk of conversion to the full mutation.