In the synthesis-dependent strand-annealing (SDSA) model of D-loop resolution, D-loop strands extended by DNA repair synthesis dissociate from their sister chromatid complements and reanneal with their original complementary strands, resulting in non-crossover products (Mitchel et al. 2010). SDSA is promoted by the DNA helicase RTEL1 (Barber et al. 2008, Uringa et al. 2012). Additional DNA synthesis occurs to fill the remaining single strand gap present in the reannealed DNA duplex. DNA polymerase alpha has been implicated in this late step of DNA repair synthesis (Levy et al. 2009), although RTEL1-mediated recruitment of PCNA-bound DNA polymerases may also be involved (Vannier et al. 2013). The remaining single strand nicks are closed by DNA ligases, possibly LIG1 or LIG3 (Mortusewicz et al. 2006, Puebla-Osorio et al. 2006).