Genetic assays for triplet repeat instability in yeast.

The unusual genetic features of trinucleotide repeat (TNR) diseases have stimulated a substantial body of research into the underlying molecular mechanisms of repeat instability. As one useful tool to study TNR instability, selectable genetic assays for expansions and contractions were developed in the yeast Saccharomyces cerevisiae. These assays are sensitive, quantitative, easy to manipulate, and reproducible. Once colonies are identified through genetic selection, follow-up experiments with PCR help detail the precise molecular changes that occurred at the TNR tract. This chapter describes these yeast assays and provides useful technical insights into creating and testing triplet repeat instability in a classic model system.