Following double strand break (DSB) formation and strand resection, Rad51 and Dmc1 coat single-stranded 3' ends of DNA and catalyze the search for homology and strand invasion into the DNA duplex of the chromosomal homolog (Barlow et al. 1997). The invading strand displaces the original strand of the chromosomal homolog creating a D-loop structure. Other proteins in the complex are inferred from cytology (Barlow et al. 1997, Plug et al. 1997, Plug et al. 1998, Moens et al. 2002).