crossovers

Definition: With the acceptance of the chromosome theory, the term is applied to the breaking during meiosis of one maternal and one paternal chromosome, the exchange of corresponding sections of DNA, and the rejoining of the chromosomes.

This process can result in an exchange of alleles between chromosomes and gives rise to new character combinations. Compare recombination. The term coined by Morgan and Cattell (1912) for the occurrence of new combinations of linked characters.

Crossovers (COs) are essential for meiosis and contribute to genome diversity by promoting the reassociation of alleles, and thus improve the efficiency of selection.

COs are not randomly distributed but are found at specific regions, or CO hotspots.

CO hotspots are highly dynamic, as shown by differences in activity between individuals, populations and closely related species.

References

 Buard J, de Massy B. Playing hide and seek with mammalian meiotic crossover hotspots. Trends Genet. 2007 Apr 12; PMID: 17434233