Figure 2.

Replication-associated recombinational repair processes. Upon encountering DNA template lesions, replication forks stall and can be repaired by multiple modes of recombinational repair. The template switch pathway (left) uses the homologous sequence on the sister chromatid as a template to replicate over the damaged region. The fork regression pathway (middle) entails the dissociation of nascent strands from their templates and their annealing with each other. One of the nascent strands can utilize the other as a template for limited DNA synthesis and/or invade the homologous template strand, forming recombination intermediates. In other situations, replication may resume downstream of a template lesion, leaving behind an ssDNA gap (right). Such a gap can be filled through recombination using the sister chromatid as a template. All three situations depicted generate DNA intermediates in the form of joint molecules, which must be processed through dissolution or resolution. It is of note that only one possible model for each situation is shown here, though others are also feasible.