Genetic recombination
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201906930
2008-03-29T22:22:32Z
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'''Genetic recombination''' is the process by which a strand of genetic material (usually [[DNA]]; but can also be [[RNA]]) is broken and then joined to a different DNA molecule. In [[eukaryotes]] recombination commonly occurs during [[meiosis]] as [[chromosomal crossover]] between paired chromosomes. This process leads to offspring having different combinations of genes from their parents and can produce new chimeric [[alleles]]. In evolutionary biology this shuffling of genes is thought to have many advantages, including that of allowing sexually reproducing organisms to avoid [[Muller's ratchet]].
In [[molecular biology]] "recombination" can also refer to artificial and deliberate recombination of disparate pieces of DNA, often from different organisms, creating what is called [[recombinant DNA]].
[[Enzyme]]s called ''[[recombinases]]'' [[Catalysis|catalyze]] natural recombination reactions. [[RecA]], the recombinase found in [[Escherichia coli|E. coli]], is responsible for the repair of DNA double strand breaks (DSBs). In yeast and other [[eukaryote|eukaryotic]] organisms there are two recombinases required for repairing DSBs. The [[RAD51]] protein is required for [[Mitosis|mitotic]] and [[Meiosis|meiotic]] recombination and the [[DMC1 (protein)|DMC1]] protein is specific to meiotic recombination.
==Chromosomal crossover==
{{main|Chromosomal crossover}}
[[Image:Morgan crossover 1.jpg|thumb|Thomas Hunt Morgan's illustration of crossing over (1916)]]
'''Chromosomal crossover''' refers to recombination between the paired [[chromosome]]s inherited from each of one's parents, generally occurring during [[meiosis]]. During [[Meiosis#Prophase I|prophase I]] the four available [[chromatid]]s are in tight formation with one another. While in this formation, [[homology (biology)|homologous]] sites on two chromatids can mesh with one another, and may exchange genetic information.
Because recombination can occur with small probability at any location along chromosome, the [[recombination frequency|frequency of recombination]] between two locations depends on their distance. Therefore, for genes sufficiently distant on the same chromosome the amount of crossover is high enough to destroy the correlation between [[alleles]].
==Gene Conversion==
{{main|Gene conversion}}
In gene conversion, a section of genetic material is copied from one chromosome to another, but leaves the donating chromosome unchanged.
==Nonhomologous recombination==
{{main|Non-homologous end joining}}
Recombination can occur between DNA sequences that contain no sequence [[homology (biology)|homology]]. This is referred to as ''Nonhomologous recombination'' or [[Non-homologous end joining|nonhomologous end joining]].
==See also==
*[[Recombination frequency]]
*[[Recombination hotspot]]
*[[Four Gamete Test]]
==External links==
*[http://www.mun.ca/biochem/courses/3107/Lectures/Topics/Recombination_holliday.html The Holliday Model of Genetic Recombination]
*{{MeshName|Genetic+recombination}}
*[http://www.blackwellpublishing.com/trun/artwork/Animations/Recombination/recombination.html Animated guide to homologous recombination.]
==References==
*Alberts, B. et al., ''Molecular Biology of the Cell'', 3rd Edition. Garland Publishing, 1994.
{{NCBI-scienceprimer}}
{{Genetic recombination}}
[[Category:Cellular processes]]
[[Category:Molecular genetics]]
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