Presenter(s): Anna Horacek
Faculty Mentor(s): Diana Libuda & Erik Toraason
Oral Session 3 M
Poster 68
Session: Sciences
Most sexually reproducing organisms utilize meiosis, a specialized form of cell division, to generate haploid gametes such as eggs and sperm. Meiotic cells utilize recombination to repair double-strand DNA breaks (DSBs) with either the sister chromatid or homologous chromosome as a repair template. Although recombination with the homologous chromosome has been extensively studied, little is known about engagement of the sister chromatid during meiotic DSB repair. To characterize sister chromatid recombination, we have developed a sister chromatid repair (SCR) assay in Caenorhabditis elegans. The SCR assay contains engineered nucleotide polymorphisms enabling the detection of gene conversions between sister chromatids, which arise from the nonreciprocal exchange of sequences between chromosome templates and indicate recombination intermediates. Analysis of these conversions tracts indicate that throughout meiotic prophase I: 1) sister chromatid repair intermediates remain central to the site of DSB induction; and, 2) sister chromatid repair is highly processive, as template switching is not observed. Interestingly, the length of conversion tracts, indicating the extent of DSB resectioning, changes in the presence of a homolog repair template. In the absence of a homolog repair template, the conversion tract size is uniform throughout prophase I. When a homolog repair template is present, large conversion tracts (>210bp) are observed only in late prophase I, suggesting the presence of the homolog repair template may affect the extent of DSB resectioning in late prophase I. Taken together, our work presents a comprehensive analysis of meiotic sister chromatid recombination and defines mechanisms fundamental to the preservation of genomic integrity.