Editing Sex (section)

=== Genetic ===
==== XY sex determination ====
[[File:Drosophila XY sex-determination.svg|thumb|The common fruit fly has an [[XY sex-determination system]], as do humans and most mammals.]]
Humans and most other [[mammal]]s have an [[XY sex-determination system]]: the [[Y chromosome]] carries factors responsible for triggering male development, making XY sex determination mostly based on the presence or absence of the [[Y chromosome]]. It is the male [[gamete]] that determines the sex of the offspring.<ref name="Wallis-2008">{{cite journal|vauthors=Wallis MC, Waters PD, Graves JA|date=October 2008|title=Sex determination in mammals – before and after the evolution of SRY|journal=Cellular and Molecular Life Sciences|volume=65|issue=20|pages=3182–95|doi=10.1007/s00018-008-8109-z|pmid=18581056|s2cid=31675679|pmc=11131626}}</ref> In this system XX mammals typically are female and XY typically are male.<ref name="Bachtrog-2014" /> However, individuals with [[Klinefelter syndrome|XXY]] or [[XYY syndrome|XYY]] are males, while individuals with [[Turner syndrome|X]] and [[Triple X syndrome|XXX]] are females.<ref name="Hake-2008" /> Unusually, the [[platypus]], a [[monotreme]] mammal, has ten sex chromosomes; females have ten X chromosomes, and males have five X chromosomes and five Y chromosomes. Platypus egg cells all have five X chromosomes, whereas sperm cells can either have five X chromosomes or five Y chromosomes.<ref>{{cite book | vauthors = Pierce BA |title=Genetics: a conceptual approach |date=2012 |publisher=W.H. Freeman |isbn=978-1-4292-3250-0 |edition=4th |location=New York |pages=73–74 |oclc=703739906}}</ref>

XY sex determination is found in other organisms, including insects like the [[Drosophila melanogaster|common fruit fly]],<ref name="Kaiser-2010">{{cite journal|vauthors=Kaiser VB, Bachtrog D|year=2010|title=Evolution of sex chromosomes in insects|journal=Annual Review of Genetics|volume=44|pages=91–112|doi=10.1146/annurev-genet-102209-163600|pmc=4105922|pmid=21047257}}</ref> and some plants.<ref name="Dellaporta-1993">{{cite journal | vauthors = Dellaporta SL, Calderon-Urrea A | title = Sex determination in flowering plants | journal = The Plant Cell | volume = 5 | issue = 10 | pages = 1241–1251 | date = October 1993 | pmid = 8281039 | pmc = 160357 | doi = 10.1105/tpc.5.10.1241 | jstor = 3869777 }}</ref> In some cases, it is the number of X chromosomes that determines sex rather than the presence of a Y chromosome.<ref name="Hake-2008" /> In the fruit fly individuals with XY are male and individuals with XX are female; however, individuals with XXY or XXX can also be female, and individuals with X can be males.<ref>{{cite book| vauthors = Fusco G, Minelli A |author-link2=Alessandro Minelli (biologist) |url={{GBurl|id=AKGsDwAAQBAJ}}|title=The Biology of Reproduction|year=2019|publisher=Cambridge University Press|isbn=978-1-108-49985-9|pages=306–308 }}</ref>

==== ZW sex determination ====
In birds, which have a [[ZW sex-determination system]], the W chromosome carries factors responsible for female development, and default development is male.<ref>{{cite journal | vauthors = Smith CA, Katz M, Sinclair AH | title = DMRT1 is upregulated in the gonads during female-to-male sex reversal in ZW chicken embryos | journal = Biology of Reproduction | volume = 68 | issue = 2 | pages = 560–570 | date = February 2003 | pmid = 12533420 | doi = 10.1095/biolreprod.102.007294 | doi-access = free }}</ref> In this case, ZZ individuals are male and ZW are female. It is the female [[gamete]] that determines the sex of the offspring. This system is used by birds, some fish, and some [[crustacean]]s.<ref name="Hake-2008" />

The majority of [[Lepidoptera|butterflies and moths]] also have a ZW sex-determination system. Females can have Z, ZZW, and even ZZWW.<ref>{{cite book| vauthors = Majerus ME | author-link = Michael Majerus |url= {{GBurl|id=vDHOYPQ2mmYC|q=ZW+sex+determination}}|title=Sex Wars: Genes, Bacteria, and Biased Sex Ratios|date=2003|publisher=Princeton University Press|isbn=978-0-691-00981-0|page=59|language=en}}</ref>

==== XO sex determination ====
In the [[XO sex-determination system]], males have one X chromosome (XO) while females have two (XX). All other chromosomes in these diploid organisms are paired, but organisms may inherit one or two X chromosomes. This system is found in most [[arachnid]]s, insects such as [[silverfish]] ([[Apterygota]]), [[dragonfly|dragonflies]] ([[Paleoptera]]) and [[grasshopper]]s ([[Exopterygota]]), and some nematodes, crustaceans, and gastropods.<ref name="Bull-1983">{{cite book|title=Evolution of sex determining mechanisms|vauthors=Bull JJ|year=1983|isbn=0-8053-0400-2|page=17|publisher=Benjamin/Cummings Publishing Company, Advanced Book Program |author-link=James J. Bull}}</ref><ref>{{cite journal|vauthors=Thiriot-Quiévreux C|date=2003|title=Advances in chromosomal studies of gastropod molluscs.|journal=Journal of Molluscan Studies|volume=69|issue=3|pages=187–202|doi=10.1093/mollus/69.3.187|doi-access=free}}</ref>

In [[Gryllus|field cricket]]s, for example, insects with a single X chromosome develop as male, while those with two develop as female.<ref>{{cite journal |title=Karyotypes of two American field crickets: Gryllus rubens and Gryllus sp. (Orthoptera: Gryllidae) | vauthors = Yoshimura A |journal=Entomological Science |volume=8 |issue=3 |pages=219–222 |year=2005 |doi=10.1111/j.1479-8298.2005.00118.x| s2cid = 84908090 }}</ref>

In the nematode ''[[Caenorhabditis elegans]]'', most worms are self-fertilizing hermaphrodites with an XX karyotype, but occasional abnormalities in chromosome inheritance can give rise to individuals with only one X chromosome—these XO individuals are fertile males (and half their offspring are male).<ref>{{cite book|title=''C. elegans'' II|vauthors=[[Barbara J. Meyer|Meyer BJ]]|publisher=Cold Spring Harbor Laboratory Press|year=1997|isbn=978-0-87969-532-3|veditors=Riddle DL, Blumenthal T, Meyer BJ, Priess JR|chapter=Sex Determination and X Chromosome Dosage Compensation: Sexual Dimorphism|chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK20094/|access-date=17 April 2021|archive-date=6 May 2021|archive-url=https://web.archive.org/web/20210506154914/http://www.ncbi.nlm.nih.gov/books/NBK20094/|url-status=live}}</ref>

==== ZO sex determination ====
In the [[ZO sex-determination system]], males have two Z chromosomes whereas females have one. This system is found in several species of moths.<ref>{{cite book | vauthors = De Prins J, Saithoh K | chapter = Karyology and Sex Determination |chapter-url={{GBurl|id=5w8FgSGuH34C|q=ZO+sex-determination+system+moth|p=461}} | veditors =  Kristensen N |title=Handbuch Der Zoologie / Handbook of Zoology | volume = Arthropoda: Insecta: Lepidoptera, Moths and Butterflies |publisher=Walter de Gruyter|year=2003 | pages = 449–468 | doi = 10.1515/9783110893724.449 |isbn=978-3-11-016210-3|access-date=29 September 2020|via=Google Books}}</ref>