Genetic Crossing Over
The reciprocal exchange of segments at corresponding positions along pairs of homologous chromosomes by symmetrical breakage and crosswise rejoining forming cross-over sites (Holliday junctions) that are resolved during chromosome segregation. Crossing-over typically occurs during meiosis but it may also occur in the absence of meiosis, for example, with bacterial chromosomes, organelle chromosomes, or somatic cell nuclear chromosomes.