<P> Recombination can be artificially induced in laboratory (in vitro) settings, producing recombinant DNA for purposes including vaccine development . </P> <P> V (D) J recombination in organisms with an adaptive immune system is a type of site - specific genetic recombination that helps immune cells rapidly diversify to recognize and adapt to new pathogens . </P> <P> During meiosis, synapsis (the pairing of homologous chromosomes) ordinarily precedes genetic recombination . </P> <P> Genetic recombination is catalyzed by many different enzymes . Recombinases are key enzymes that catalyse the strand transfer step during recombination . RecA, the chief recombinase found in Escherichia coli, is responsible for the repair of DNA double strand breaks (DSBs). In yeast and other eukaryotic organisms there are two recombinases required for repairing DSBs . The RAD51 protein is required for mitotic and meiotic recombination, whereas the DNA repair protein, DMC1, is specific to meiotic recombination . In the archaea, the ortholog of the bacterial RecA protein is RadA . </P>

What occurs to molecules of dna during mitosis