Recombinational repair is a DNA repair mechanism where one strand contains damage and another strand does not, after semi-conservative replication.
RecA recombinase catalyses this process, identifying the gap left in the DNA strand by the DNA polymerase. Regions of homology are identified by RecA, which are then aligned, before strand invasion is initiated. This involves inserting the complementary section of DNA from the undamaged strand into the damaged strand. This is used when thymine dimers have not been repaired by nucleotide excision repair, among other errors.
After the complementary section has been inserted, nucleotide excision repair is used to repair the damaged base, and then DNA polymerase and ligase fills the gap and forms phosphodiester bonds in the sugar-phosphate backbone of the DNA molecules.