Schematic representation of the model showing repair of DSBs by homologous recombination. When a DSB occurs, it is processed to generate 3' single-stranded ends. RAD51 nucleoprotein microfilament is assembled on these ends, one of which invades the homologous DNA by strand displacement. This results in the formation of the D-loop. The invading strand primes DNA synthesis using the homologous DNA as a template. The second single-stranded DNA is also captured for priming DNA synthesis by using the displaced strand as a template. Extension of the 3' ends ultimately results in two cross-structures that hold the two homologs together, called Holliday junctions (HJs). Migration of HJs, called branch migration, results in the formation of heteroduplex regions. The double HJs are resolved by resolvases and, depending on the cleavage site, can either lead to crossover or non-crossover products. Resolution to yield crossover products requires symmetric cleavage of both HJs in opposite orientations.