Fig. 1.

DSB repair in the S and G2 phases of the cell cycle. In late S and the G2 phase of the cell cycle, DSBs can be repaired by homologous recombination (HR) using the undamaged sister chromatid. In the initial stage of HR, the ends of the DSBs are resected to generate 3′ single stranded regions. If the ends are resected but HR is inactivated, the DSBs can be joined by back-up pathways, single strand annealing and alternative non-homologous end joining. In contrast to the error-free homolgous recombination pathways, the back-up pathways generate genomic rearrangements