DESCRIPTION (provided by applicant): Recombination is both a means to avoid genome instability and to a process that generates genome instability. In meiosis, DNA double-strand breaks are repaired into crossovers that are essential for accurate segregation of homologous chromosomes; defects in this process result in sterility or aneuploidy, the major cause of pregnancy loss and trisomy. Conversely, in mitotically proliferating cells double-strand breaks are a dangerous class of DNA damage. Repair of breaks in this context is done without making crossovers; formation of crossovers in mitotic cells can lead to chromosome rearrangements and tumorigenesis. Research in my laboratory focuses on mechanisms that promote crossovers in meiotic cells and non-crossover outcomes of repair in mitotic cells. We focus on helicases that disassemble recombination intermediates to generate non-crossovers and Holliday junction resolvases that cleave intermediates and can generate crossovers. Our central approach is to take advantage of unique features of Drosophila to address important questions that are difficult to answer with other model systems. In addition, we have developed repair assays to use in human cells, done in vitro biochemical studies, and begun deep sequencing projects. This combination of approaches will help to continue to drive the recombination field forward.

PUBLIC HEALTH RELEVANCE Genetic exchange between homologous chromosomes is essential to ensure that they segregate accurately in meiosis, the specialized cell division that gives rise to eggs and sperm. Errors in recombination can lead to aneuploidy, which is the most common cause of birth defects and miscarriage, however, the same type of exchange in other cells can lead to cancer. This proposal seeks to understand how exchange is promoted in cells undergoing meiosis but avoided in other tissues.