Figure 6.

Homologous recombination. Repair of a double-strand break (DSB) by homologous recombination typically yields either a crossover (CO) or a noncrossover gene conversion (NCO). COs exhibit a Mendelian, or 2:2, segregation pattern of alleles, while NCOs exhibit a 1:3 segregation pattern of the alleles covered by the NCO. In flies, NCOs may be formed by synthesis-dependent strand annealing (SDSA) or by a modified version of SDSA in which both ends of the break engage with the homolog. Other, more complex outcomes of repair by gene conversion have also been observed in Drosophila (Crown et al. 2014).