The Rad51 and Dmc1 recombinases: a non-identical twin relationship

A double-strand break in genomic DNA that remains unrepaired can be lethal for a cell, indeed, the integrity of the genome is paramount for survival. It is therefore surprising that some cells deliberately introduce double-st rand breaks at certain times during their life cycle. Why might they do thi s? What are the benefits? How are these breaks repaired? The answers to the se questions lie in understanding the basis of meiotic recombination, the p rocess that leads to genetic variation. This review summarizes the key role s played by the two recombinases, Dmc1 and Rad51, in the faithful repair of DNA breaks.