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. Author manuscript; available in PMC: 2017 Sep 1.
Published in final edited form as: Trends Genet. 2016 Jul 19;32(9):566–575. doi: 10.1016/j.tig.2016.06.007

Figure 3.

Figure 3

Shown is a model for the influence of cell cycle phase and the presence of the sister chromatid on DSB repair pathways. G1 phase is shown as being suppressed for end resection, such that a DSB in this context would likely be repaired by C-NHEJ. S/G2 phases are shown as permissive for end resection. The middle chromosome diagram shows a DSB occurring in S-phase but before this particular chromosome (or at least the region at the DSB) has been replicated. In this context, the sister chromatid is unavailable for HDR, such that if this DSB is resected, it will likely be repaired by SSA or ALT-EJ. In contrast, the chromosome on the right has been replicated prior to DSB formation, such that HDR with the sister chromatid template is feasible. Thus, HDR is depicted as favored in this context over SSA or ALT-EJ (i.e. the solid line versus the dashed lines). Also shown is the notion that DSBs are not necessarily end resected in S/G2, such that C-NHEJ is active throughout the cell cycle.