Non allelic homologous recombination

Non allelic homologous recombination (NAHR) is a form of homologous recombination that occurs between two lengths of DNA that have high sequence homology, but are not alleles.^[1][2]

It usually occurs between sequences of DNA that have been previously duplicated through evolution, and therefore have low copy repeats (LCRs). When non allelic homologous recombination occurs between different LCRs, deletions or further duplications of the DNA can occur. This can give rise to rare genetic disorders, caused by the loss or increased copy number of genes within the deleted or duplicated region. It can also contribute to the copy number variation seen in some gene clusters.^[3]

As LCRs are often found in "hotspots" in the human genome, some chromosomal regions are particularly prone to NAHR. ^[1] Therefore multiple patients may manifest with similar deletions or duplications, resulting in the description of genetic syndromes. Examples of these include NF1 microdeletion syndrome, 17q21.3 recurrent microdeletion syndrome or 3q29 microdeletion syndrome.^[4][5][6]

See also

• Genetic recombination
• Non-homologous end joining

References

1. ^ ^{a b} Hurles, Matthew, et al (2006), "Recombination Hotspots in Nonallelic Homologous Recombination", Genomic Disorders: The Genomic Basis of Disease, Humana Press, pp. 341–355, http://www.springerlink.com/content/um222230u28p1719/ 
2. ^ Beckmann JS, Estivill X, Antonarakis SE (August 2007). "Copy number variants and genetic traits: closer to the resolution of phenotypic to genotypic variability". Nat. Rev. Genet. 8 (8): 639–46. doi:10.1038/nrg2149. PMID 17637735. 
3. ^ Karn RC, Laukaitis CM (2009). "The mechanism of expansion and the volatility it created in three pheromone gene clusters in the mouse (Mus musculus) genome". Genome Biol Evol 1: 494–503. doi:10.1093/gbe/evp049. PMC 2839280. PMID 20333217. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2839280. 
4. ^ Venturin M, Gervasini C, Orzan F, et al. (June 2004). "Evidence for non-homologous end joining and non-allelic homologous recombination in atypical NF1 microdeletions". Hum. Genet. 115 (1): 69–80. doi:10.1007/s00439-004-1101-2. PMID 15103551. 
5. ^ Koolen DA, Sharp AJ, Hurst JA, et al. (November 2008). "Clinical and molecular delineation of the 17q21.31 microdeletion syndrome". J. Med. Genet. 45 (11): 710–20. doi:10.1136/jmg.2008.058701. PMID 18628315. 
6. ^ Willatt L, Cox J, Barber J, et al. (July 2005). "3q29 microdeletion syndrome: clinical and molecular characterization of a new syndrome". Am. J. Hum. Genet. 77 (1): 154–60. doi:10.1086/431653. PMC 1226188. PMID 15918153. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1226188.