Following branch migration, the invading 3' resected ssDNA end of the double-strand break (DSB) acts as a primer for repair DNA synthesis using the complementary strand of the invaded duplex as a template. The replicative DNA polymerases delta (POLD) and likely epsilon (POLE), as well as translesion synthesis (TLS) DNA polymerases eta (POLH) and kappa (POLK) in complex with PCNA, RFC and RPA are implicated in DNA repair synthesis and D-loop extension. While TLS polymerases increase the efficiency of homologous recombination-related DNA synthesis and can directly interact with D-loop proteins RAD51, PALB2 and BRCA2, it is likely that replicative DNA polymerases POLD and POLE, with their high processivity and fidelity, perform the major role in D-loop extension (McIlwraith et al. 2005, Sebesta et al. 2013, Pomerantz et al. 2013, Buisson et al. 2014). In addition, the presence of RAD51-translocases, homologous to yeast Rad54, that remove RAD51 from the 3' invading strand, may be necessary for the catalytic activity of POLD or POLE (Li et al. 2009, Li and Heyer 2009).