Editing XY sex-determination system (section)

=== Mammals ===
In most mammals, sex is determined by presence of the Y chromosome. This makes individuals with [[Klinefelter syndrome|XXY]] and [[XYY syndrome|XYY]] karyotypes males, and individuals with [[Turner syndrome|X]] and [[Trisomy X|XXX]] karyotypes females.<ref name="Hake-2014" />

In the 1930s, [[Alfred Jost]] determined that the presence of [[testosterone]] was required for [[Wolffian duct]] development in the male rabbit.<ref name="Jost-1970">{{cite journal | vauthors = Jost A | title = Hormonal factors in the sex differentiation of the mammalian foetus | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 259 | issue = 828 | pages = 119–130 | date = August 1970 | pmid = 4399057 | doi = 10.1098/rstb.1970.0052 | bibcode = 1970RSPTB.259..119J | doi-access = free | jstor = 2417046 }}</ref>

SRY is a sex-determining gene on the Y chromosome in the [[theria]]ns (placental mammals and marsupials).<ref name="Wallis-2008">{{cite journal | vauthors = Wallis MC, Waters PD, Graves JA | title = Sex determination in mammals--before and after the evolution of SRY | journal = Cellular and Molecular Life Sciences | volume = 65 | issue = 20 | pages = 3182–3195 | date = October 2008 | pmid = 18581056 | pmc = 11131626 | doi = 10.1007/s00018-008-8109-z | s2cid = 31675679 }}</ref> Non-human mammals use several genes on the Y chromosome.{{Citation needed|date=August 2021|reason=Your explanation here}}

Not all male-specific genes are located on the [[Y chromosome]]. The [[platypus]], a [[monotreme]], use five pairs of different XY chromosomes with six groups of male-linked genes, [[Anti-Müllerian hormone|AMH]] being the master switch.<ref>{{cite journal | vauthors = Cortez D, Marin R, Toledo-Flores D, Froidevaux L, Liechti A, Waters PD, Grützner F, Kaessmann H | title = Origins and functional evolution of Y chromosomes across mammals | journal = Nature | volume = 508 | issue = 7497 | pages = 488–493 | date = April 2014 | pmid = 24759410 | doi = 10.1038/nature13151 | url = https://odin.mdacc.tmc.edu/~ryu/materials/papers/nature2014April_EvolutionYChrom.pdf | url-status = live | bibcode = 2014Natur.508..488C | s2cid = 4462870 | s2cid-access = free | archive-url = https://web.archive.org/web/20170810203303/http://odin.mdacc.tmc.edu/~ryu/materials/papers/nature2014April_EvolutionYChrom.pdf | archive-date = Aug 10, 2017 }}</ref>

====Humans====
[[File:Human male karyotpe high resolution - XY chromosome cropped.JPG|thumb|199px|Human male XY chromosomes after [[G-banding]]]]
A single gene (''[[SRY]]'') present on the Y chromosome acts as a signal to set the developmental pathway towards maleness. Presence of this gene starts off the process of [[virilization]]. This and other factors result in the [[sex differences in humans]].<ref name="Fauci-2008">{{Cite book|title = Harrison's Principles of Internal Medicine|url = https://archive.org/details/harrisonsprincip00asfa|url-access = limited| vauthors = Fauci AS, Braunwald E, Kasper DL, Hauser SL, Longo DL, Jameson JL, Loscalzo J |publisher = McGraw-Hill Medical|year = 2008|isbn = 978-0-07-147693-5|pages = [https://archive.org/details/harrisonsprincip00asfa/page/n2377 2339]–2346 |edition = 17th }}</ref> The cells in females, with two X chromosomes, undergo [[X-inactivation]], in which one of the two X chromosomes is inactivated. The inactivated X chromosome remains within a cell as a [[Barr body]].