Crossing over is a basic concept ofgenetics andcell biology, often calledrecombination. It occurs duringmeiosis.
Crossing over is the exchange ofchromosome segments between non-sisterchromatids during the production ofgametes. The effect is to assort (shuffle) thealleles on parental chromosomes, so that the gametes carrycombinations ofgenes different from either parent. This has the overall effect of increasing the variety ofphenotypes present in a population.
The process can be seen directly in stainedcells, and indirectly if there are genetic markers or not on the chromosomes. The visiblecrossovers are calledchiasma (plural:chiasmata), which isGreek for a cross. F. A. Janssens was the first to suggest what chiasmata meant.[1][2]
The large-scale effect of crossing over is to spread variation through a population. This is the main result of sexual reproduction compared to non-sexual modes of reproduction.
The main advantage to the parents is the greater variety in their offspring. This, it is thought, increases the chance that some of the offspring will survive and reproduce. This has been the subject of much investigation and discussion.[3]
