Rad51 is a eukaryotic homologue of E. coli RecA, a recombinase, and a component of the homologues recombination DNA repair pathway.  Rad51 forms a nucleoprotein filament through binding Rad52 and single stranded DNA that are exposed following double strand breaks.  This filament initiates recombination.  Rad 51B, Rad51C, Rad51D, XRCC2 and XRCC3 (X-Ray Repair Cross Complementing 2 and 3) are Rad51 paralogs and are also components of the homologous recombination pathway