recA‐dependent DNA repair processes

UV‐radiation‐induced lesions in DNA result in the formation of: (1) excision gaps (i.e. a lesion is excised, leaving a gap), (2) daughter‐strand gaps (i.e. a lesion can be skipped during replication, leaving a gap), and (3) double‐strand breaks (i.e. the DNA strand opposite a gap can be cut). In Escherichia coli, the recA gene product is involved in repairs of all three types of lesions – repair of daughter‐strand gaps (2) and double‐strand breaks (3) constitutes post‐replication repair. The evidence suggests, furthermore, that recA‐dependent repair of excision gaps 1 produced in DNA replicated prior to UV irradiation (pre‐replication repair) appears to occur by similar mechanisms.