Homologous recombination is needed for meiotic chromosome segregation, genome maintenance, and tumor suppression. RAD51AP1 (RAD51 A&barbelow;ssociated P&barbelow;rotein 1) interacts with and enhances the recombinase activity of RAD51. Accordingly, genetic ablation of RAD51API leads to enhanced sensitivity to and also chromosome aberrations upon DNA damage, demonstrating a role for RAD51AP1 in mitotic homologous recombination. My work in this thesis used biochemical methods to further understand the mechanistic role of RAD51AP1 in homologous recombination. I show that the DNA binding activity of RAD51AP1 is required, along with its RAD51 binding activity, for effective enhancement of RAD51. Interestingly, RAD51AP1 was found to also interact with and stimulate the meiotic recombinase, DMC1. Although DMC1 and RAD51 are highly similar in their sequence and homologous DNA pairing activities, RAD51AP1 interacts with each recombinase interaction through separate epitopes. I also demonstrated the abundant expression of RAD51AP1 in meiotic cells where DMC1 is present, and the colocalization of both proteins to recombination centers on meiotic chromatin. Thus, my thesis work suggests that RAD51AP1 plays an important role in mitotic and meiotic homologous recombination pathways by directly regulating the RAD51 and DMCI recombinases.