My lab uses the yeast Saccharomyces cerevisiae as a model organism to study genome instability. In particular, we are investigating the molecular basis of two related types of DNA mutations: repeat expansions and chromosome fragility. Expansion of repeat sequences is the cause of more than 20 inherited diseases including Huntington's disease (a degenerative neurological disease), Fragile X syndrome (the most common inherited mental retardation), and myotonic dystrophy (a type of muscular dystrophy). We are investigating the mechanism of repeat expansions during DNA replication and DNA repair, and the effect of chromatin state of the likelihood of repeat expansion. In addition, we are investigating the basis of chromosome fragility and its implications for cell growth and survival. The causes of chromosome fragility are not well understood, but the results can be significant: a broken chromosome is vulnerable to loss or rearrangement, which can lead to genomic changes and cancer. Our results in this area could shed light on the genomic instability that occurs in repeat expansion diseases as well as during tumorigenesis.