Research Summary Recombination between chromosomes is required to generate genetic variation, maintain genome integrity, and ensure proper chromosome segregation during meiosis, the specialized cell division program that generates haploid gametes such as sperm and eggs. Perturbations in recombination can compromise these basic cellular functions, ultimately leading to cancer, infertility, or birth defects. Meiotic recombination is initiated by programmed double strand DNA breaks (DSBs), which are repaired using meiosis-specific mechanisms that 1) favor utilization of the homologous chromosome (instead of the sister chromatid) as the repair partner; and, 2) promote a crossover outcome of the DSB repair process, which is required for proper chromosome segregation during meiosis. Although repair of DSBs with the appropriate template (homologous chromosome) is necessary for proper chromosome segregation and genome integrity, our knowledge of how germ cells achieve this critical template preference in the presence of nearly identical sequences (sister chromatids) is limited due to assay limitations in metazoans. The goal of our research program is to understand how chromosomes are able to access distinct recombination pathways and partners to ensure faithful genome inheritance. Using in vivo assays we developed in the model system Caenorhabditis elegans, we have directly detected and analyzed use of the sister chromatid as a repair template during metazoan meiotic prophase I progression. Building upon our published work, we are defining and establishing how specific chromosome structures, proteins, and cellular contexts regulate recombination pathway and repair partner choices to maintain meiotic genome integrity. As articulated in the PEDP of the parent award, the PI is firmly dedicated to mentoring and diversifying science with deliberate and purposeful efforts to promote inclusive excellence within science within the planned research program. With this administrative supplement, we will expand our mentoring and research studies in the parent award to define the factors that impact the sexually dimorphic crossover recombination landscape, and to determine the role of actin polymerization in DSB repair during meiotic prophase I. Overall, these studies will reveal how recombination pathway and partner choices ensure that chromosomes form the connections necessary for chromosome segregation and repair DSBs for maintaining genomic integrity during sperm and egg development.