Ectopic recombination is an atypical form of recombination in which a crossing over takes place between two homologous DNA sequences located at non-allelic chromosomal positions. Such recombination often results in dramatic chromosomal rearrangement, which is generally harmful to the organism.[1] Some research, however, has suggested that ectopic recombination can result in mutated chromosomes that benefit the organism.[2] Ectopic recombination can occur during both meiosis and mitosis, although it is more likely occur during meiosis.[3] It occurs relatively frequently—in at least one yeast species (Saccharomyces cerevisiae) the frequency of ectopic recombination is roughly on par with that of allelic (or traditional) recombination.[4] If the alleles at two loci are heterozygous, then ectopic recombination is relatively likely to occur, whereas if the alleles are homozygous, they will almost certainly undergo allelic recombination.[4] Ectopic recombination does not require loci involved to be close to one another; it can occur between loci that are widely separated on a single chromosome, and has even been known to occur across chromosomes.[5] Neither does it require high levels of homology between sequences—the lower limit required for it to occur has been estimated at as low as 2.2 kb of homologous stretches of DNA nucleotides.[4]
In tobacco plant somatic cells, DNA double-strand break-induced recombination between ectopic homologous sequences appears to serve as a minor DNA repair pathway for double-strand breaks.[6]
The role of transposable elements in ectopic recombination is an area of active inquiry. Transposable elements—repetitious sequences of DNA that can insert themselves into any part of the genome—can encourage ectopic recombination at repeated homologous sequences of nucleotides. However, according to one proposed model, ectopic recombination might serve as an inhibitor of high transposable element copy numbers.[1] The frequency of ectopic recombination of transposable elements has been linked to both higher copy numbers of transposable elements and the longer lengths of those elements.[7] Since ectopic recombination is generally deleterious, anything that increases its odds of occurring is selected against, including the aforementioned higher copy numbers and longer lengths. This model, however, can only be applied to single families of transposable elements in the genome, as the probability of ectopic recombination occurring in one TE family is independent of it occurring in another. It follows that transposable elements that are shorter, transpose themselves less often, and have mutation rates high enough to disrupt the homology between transposable element sequences sufficiently to prevent ectopic recombination from occurring are selected for.[7]
^ abMontgomery, E., B. Charlesworth, and C. H. Langley. 1987. A test for the role of natural selection in the stabilization of transposable element copy number in a population of Drosophila melanogaster. Genet. Res. 49:31–41
^Bush, G.L., S.M. Case, A.C. Wilson and J.L. Patton. 1977. Rapid speciation and chromosomal evolution in mammals. Proc. Natl. Acad. Sci. USA 74: 3942-3946
^Montgomery, E., S.M. Huang, C.H. Langley, and B.H. Judd. 1991. Chromosome rearrangement by ectopic recombination in drosophila melanogaster: genome structure and evolution. Genetics 129: 1085-1098
^ abcLicthen, M, R.H. Borts, and J.E. Haber. 1986. Meiotic gene conversion and crossing over between dispersed homologous sequences occurs frequently in saccharomyces cerevisiae. Genetics 115: 233-246
^Harris, S, K.S. Rudnicki, and J.E. Haber. 1993. Gene conversions and crossing over during homologous and homeologous ectopic recombination in saccharomyces cerevisiae. Genetics 135: 5-16
^Puchta H. Double-strand break-induced recombination between ectopic homologous sequences in somatic plant cells. Genetics. 1999 Jul;152(3):1173-81. doi: 10.1093/genetics/152.3.1173. PMID 10388832; PMCID: PMC1460648
^ abPetrov, D.A, Y.T. Aminetzach, J.C. Davis, D. Bensasson, and A.E. Hirsh. 2003. Size matters: non-LTR retrotransposable elements and ectopic recombination in drosophila. Mol Bio Evol 20: 880-892
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Ectopicrecombination is an atypical form of recombination in which a crossing over takes place between two homologous DNA sequences located at non-allelic...
The products of this recombination are a duplication at the site of the exchange and a reciprocal deletion. Ectopicrecombination is typically mediated...
genes to hundreds of genes. Inversions can happen either through ectopicrecombination between repetitive sequences, or through chromosomal breakage followed...
molecular evolution. Common sources of gene duplications include ectopicrecombination, retrotransposition event, aneuploidy, polyploidy, and replication...
it can recruit new exons to produce a chimeric gene. Finally, ectopicrecombination, when there is an exchange between portions of the genome that are...
silencing and protect the genome from deleterious rearrangements due to ectopicrecombination. They may also be involved in fillers for increasing chromosome...
or ectopic, meaning that one paralogous DNA sequence converts another. Allelic gene conversion occurs during meiosis when homologous recombination between...
which two or more exons from different genes can be brought together ectopically, or the same exon can be duplicated, to create a new exon-intron structure...
molecules are DNA molecules formed by laboratory methods of genetic recombination (such as molecular cloning) that bring together genetic material from...
antibiotics (Thayer–Martin). It exhibits antigenic variation through genetic recombination of its pili and surface proteins that interact with the immune system...
more very closely linked homologous genes with little or no observable recombination between them", and include the common ABO and Rh (Rhesus) antigen systems...
meiosis homologous recombination. Ectopic gene conversion occurs when one homologous DNA sequence is replaced by another. Ectopic gene conversion is the...
limitations, in the summary table below. Homologous recombination (HR) is a kind of genetic recombination in which genetic sequences are exchanged between...
pregnancy. Embryonic implantation not in the uterine wall results in an ectopic pregnancy that can kill the mother. In such animals as rabbits, coitus...
two and adding more. One theory to explain the exact specifics is that ectopic Transcriptional factors direct the cell to an earlier progenitor state...
it is when these two cells merge into one zygote cell that genetic recombination occurs and the new zygote contains 23 chromosomes from each parent,...
their maturation in the thymus, they undergo a process called V(D)J recombination which conducts the development of T cell receptors (TCRs). The mechanism...
chromosome. NHEJ is also used to repair DSBs generated during V(D)J recombination when gene regions are rearranged to create the unique antigen binding...
protein complex that mediates sister chromatid cohesion, homologous recombination, and DNA looping. Cohesin is formed of SMC3, SMC1, SCC1 and SCC3 (SA1...
one of the best targets may be a peptide domain of FANCM called MM2. Ectopic MM2 peptide (that acts as a dominant decoy) was sufficient to inhibit colony...
using vegetative mycelium. Otherwise, insertion of integrative vectors ectopically and with small homologous regions can be used, likely with low transformation...
mutagenesis mechanisms, and include the SOS response in bacteria, ectopic intrachromosomal recombination and other chromosomal events such as duplications. The sequence...
homologous gene can either be knocked out or the initial gene can be ectopically expressed in the model organism, at which point a screen for modifiers...
S2CID 229694823. Greene PJ, Sussman HH (October 1973). "Structural comparison of ectopic and normal placental alkaline phosphatase". Proceedings of the National...
Drosophila nervous system. This technique relies on recombination during mitosis mediated by FLP-FRT recombination. As one copy of a gene, provided by the balancer...
"Retrotransposition of a yeast group II intron occurs by reverse splicing directly into ectopic DNA sites". Proceedings of the National Academy of Sciences of the United...
chromosomal events seem also to be rather relevant: while an ectopic intrachromosomal recombination has been reported to be involved in acquisition of resistance...
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