Homologous Recombination is the exchange of the sequence between two associated but different DNA (or RNA) molecules, with the result that a new "chimeric" molecule is obtained. Several mechanisms might result in recombination, but a necessary requirement is the existence of the region of homology in the recombination of the partners. In DNA recombination, breakage of single strands of a DNA in the two recombination partners is followed by joining of strands present in opposing molecules, and might involve particular enzymes. Recombination of RNA molecules might occur by other mechanisms.