In eukaryotes, genetic recombination occurs in germ line cells at meiosis where it provides a mechanism for the exchange and reassortment of genetic information.
Recombination is also important in somatic cells for the repair of damaged or broken chromosomes.
Defects in recombination result in unrepaired chromosomal breaks or aberrant gene translocations, the consequences of which can be catastrophic to the cell and lead to cancer. Indeed, until recently, most of our knowledge of the molecular reactions involved in recombination was provided by studies of related processes in simple organisms. In E. coli, for example, recombination is known to require about 15 proteins. RecA, is essential for recombination and recombinational DNA repair, and has been the subject of intense study by many groups over a number of years. Our knowledge of its structure and the reactions it catalyses provides us with the stepping stone for related work with mammalian proteins.