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m →Absence of ''Spo11'' in some sexual species: Typo fixing, replaced: dessication → desiccation using AWB |
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'''Spo11''' is a [[protein]] used in a complex along with Mre11, [[RAD50 (gene)|Rad50]] and NBS1 during meiotic [[genetic recombination|recombination]].<ref name="pmid20364103">{{cite journal |vauthors=Inagaki A, Schoenmakers S, Baarends WM |title=DNA double strand break repair, chromosome synapsis and transcriptional silencing in meiosis |journal=Epigenetics |volume=5 |issue=4 |pages= 255–66|date=May 2010 |pmid=20364103 |doi= 10.4161/epi.5.4.11518|url=http://www.landesbioscience.com/journals/epi/abstract.php?id=11518 |issn=}}</ref> It is also involved in the creation of double stranded breaks in the [[DNA]] in the early stages of this process. Its active site contains a tyrosine which ligates and dissociates with DNA to promote break formation. One Spo11 protein is involved per strand of DNA, thus two Spo11 proteins are involved in each double stranded break event.
Genetic exchange between two DNA molecules by [[homologous recombination]] begins with a break in both strands of DNA—called a double-strand break—and recombination is started by an [[endonuclease]] enzyme that cuts the DNA molecule that "receives" the exchanged DNA. In [[meiosis]] the enzyme is SPO11, which is related to DNA [[topoisomerase]]s. Topoisomerases change DNA by transiently breaking one or both strands, passing the unbroken DNA strand or strands through the break and repairing the break; the broken ends of the DNA are covalently linked to topoisomerase. SPO11 is similarly attached to the DNA when it forms double-strand breaks during meiosis.<ref name="isbn0-7637-7992-X">{{cite book |title=Lewin's Genes X |edition=10th |publisher=Jones and Bartlett Publishers, Inc. |location= |year=2011 |origyear= |pages=353–354 |isbn=978-0-7637-7992-
==Meiotic recombination independent of SPO11==
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==Absence of ''Spo11'' in some sexual species==
The most recent common ancestor of the social [[amoeba]] genera ''[[Dictyostelium]]'', ''[[Polysphondylium]]'' and ''[[Acytostelium]]'', appears to have lacked the ''Spo11'' gene.<ref name=Bloomfield>{{cite journal |vauthors=Bloomfield G |title=Atypical ploidy cycles, Spo11, and the evolution of meiosis |journal=Semin. Cell Dev. Biol. |volume=54 |issue= |pages=158–64 |year=2016 |pmid=26811992 |doi=10.1016/j.semcdb.2016.01.026 |url=https://zenodo.org/record/889469}}</ref><ref name="pmid18663385">{{cite journal |vauthors=Malik SB, Pightling AW, Stefaniak LM, Schurko AM, Logsdon JM |title=An expanded inventory of conserved meiotic genes provides evidence for sex in Trichomonas vaginalis |journal=PLoS ONE |volume=3 |issue=8 |pages=e2879 |year=2007 |pmid=18663385 |pmc=2488364 |doi=10.1371/journal.pone.0002879 |url=}}</ref> Such an ancestor likely lived several hundred million years ago.<ref name="pmid24040233">{{cite journal |vauthors=Fiz-Palacios O, Romeralo M, Ahmadzadeh A, Weststrand S, Ahlberg PE, Baldauf S |title=Did terrestrial diversification of amoebas (amoebozoa) occur in synchrony with land plants? |journal=PLoS ONE |volume=8 |issue=9 |pages=e74374 |year=2013 |pmid=24040233 |pmc=3770592 |doi=10.1371/journal.pone.0074374 |url=}}</ref> ''[[Dictyostelium discoideum]]'' and ''[[Polysphondylium pallidum]]'' are both capable of [[meiosis|meiotic]] [[sexual reproduction]] (see ''[[Dictyostelium discoideum#Sexual reproduction|''D. discoideum'' sexual reproduction]]'' and ''[[Polysphondylium pallidum#Sexual reproduction|''P. pallidum'' sexual reproduction]]''). Bloomfield<ref name=Bloomfield /> speculated that dormant cells in the soil might be exposed to many kinds of stress, such as desiccation or radiation, that could induce spontaneous [[DNA damage (naturally occurring)|DNA damage]]. Such damage would make the induction of double-strand breaks by Spo11 redundant for the initiation of [[genetic recombination|recombination]] during meiosis, and thus explain its absence in this group.
==References==
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