Genetic recombination is the process by which the combination of genes in an organism's offspring becomes different from the combination of genes in that organism. This definition is commonly used in classical genetics, evolutionary biology, and population genetics.
However, in molecular biology, recombination generally refers to the molecular process by which two genes in a linkage group can become separated. One consequence of this mechanism is chromosomal crossing over, but recombination can also occur at homologous sites within one DNA molecule. Enzymes called recombinases catalyze this reaction.