Genetic recombination
Translation- Genetic recombination
Genetic recombination is the process by which a strand of genetic material (usually
DNA ; but can also beRNA ) is broken and then joined to a different DNA molecule. Ineukaryotes recombination commonly occurs duringmeiosis aschromosomal crossover between paired chromosomes. This process leads to offspring having different combinations of genes from their parents and can produce new chimericalleles . In evolutionary biology this shuffling of genes is thought to have many advantages, including that of allowing sexually reproducing organisms to avoidMuller'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 calledrecombinant DNA .Enzyme s called "recombinases " catalyze natural recombination reactions.RecA , the recombinase found in E. coli, is responsible for the repair of DNA double strand breaks (DSBs). In yeast and other eukaryotic organisms there are two recombinases required for repairing DSBs. TheRAD51 protein is required for mitotic and meiotic recombination and the DMC1 protein is specific to meiotic recombination.Chromosomal crossover
Chromosomal crossover refers to recombination between the paired
chromosome s inherited from each of one's parents, generally occurring duringmeiosis . During prophase I the four availablechromatid s are in tight formation with one another. While in this formation, 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 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
In gene conversion, a section of genetic material is copied from one chromosome to another, but leaves the donating chromosome unchanged.
Nonhomologous recombination
Recombination can occur between DNA sequences that contain no sequence homology. This is referred to as "Nonhomologous recombination" or nonhomologous end joining.
ee 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.
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