X-linked dominant inheritance: Difference between revisions

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''Main Article:'' <u>[[Sex linkage]]</u>{{short description|Mode of inheritance}}

{{refimprove|date=September 2009}}

[[File:X-linked dominant.svg|thumb|upright=1.75|X-linked dominant inheritance]]

'''X-linked dominant inheritance''', sometimes referred to as '''X-linked dominance''', is a mode of [[Genetics|genetic]] [[Heredity|inheritance]] by which a [[dominant gene]] is carried on the [[X chromosome]]. As an inheritance pattern, it is less common than the [[X-linked recessive inheritance|X-linked recessive]] type. In medicine, X-linked dominant inheritance indicates that a gene responsible for a [[genetic disorder]] is located on the X chromosome, and only one copy of the [[allele]] is sufficient to cause the disorder when inherited from a parent who has the disorder. In this case, someone who [[Gene expression|expresses]] an X-linked dominant allele will exhibit the disorder and be considered affected.{{cn|date=January 2024}} The pattern of inheritance is sometimes called ''criss-cross inheritance''.<ref>{{Cite book |last=Meneely |first=Philip Mark |url=https://www.worldcat.org/title/951645141 |title=Genetics: genes, genomes, and evolution |last2=Dawes Hoang |first2=Rachel |last3=Okeke |first3=Iruka N. |last4=Heston |first4=Katherine |date=2017 |publisher=Oxford University Press |isbn=978-0-19-879536-0 |___location=Oxford |pages=271 |oclc=951645141}}</ref>

X-linked dominant traits do not necessarily affect males more than females (unlike [[X-linked recessive]] traits). The exact pattern of inheritance varies, depending on whether the father or the mother has the trait of interest. All fathers that are affected by an X-linked dominant disorder will have affected daughters but not affected sons. However, if the mother is also affected then sons will have a chance of being affected, depending on whether a dominant or recessive X chromosome is passed on. When the son is affected, the mother will always be affected. Some X-linked dominant conditions are embryonic lethal in males, making them appear to only occur in girlsfemales.<ref>{{Cite journal |last=Wettke-Schäfer |first=Roswitha |last2=Kantner |first2=Gisela |date=July 1983 |title=X-linked dominant inherited diseases with lethality in hemizygous males |url=https://doi.org/10.1007/BF00289472 |journal=Human Genetics |language=en |volume=64 |issue=1 |pages=1–23 |doi=10.1007/BF00289472 |issn=1432-1203|url-access=subscription }}</ref>

==Genetics==

As the X chromosome is one of the [[sex chromosome]]s (the other being the [[Y chromosome]]), X-linked inheritance is determined by the [[sex]] of the parent carrying a specific gene and can often seem complex. This is due to the fact that, typically, [[female]]s have two copies of the X-chromosome, while [[male]]s have only one copy. The difference between [[Dominance (genetics)#Dominant trait|dominant]] and [[Dominance (genetics)#Recessive|recessive]] inheritance patterns also plays a role in determining the chances of a child inheriting an X-linked disorder from their parentage.{{fact|date=January 2018}}

Males can only get an X-linked chromosomedominant fromdisorders theirtend motherto whilstaffect females getmore anoften Xbecause chromosome from both parents. As a result, femalesthey tend to showbe higherdevelopmentally prevalencefatal ofin X-linkedmales. dominantThis disordersis because theymales have moreonly ofone acopy chanceof toX-chromosome inheritwhile afemales faultyhave Xtwo chromosomecopies.{{fact|date=January 2018}}

===Inheritance===

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In such a case, where both parents carry and thus are affected by an X-linked dominant disorder, the chance of a daughter receiving two copies of the X chromosome with the defective gene is 50%, since daughters receive one copy of the X chromosome from both parents. Were this to occur with an X-linked dominant disorder, that daughter would likely experience a more severe form.

Some X-linked dominant conditions such as [[Aicardi syndrome]] are fatal to boys,; therefore only girls with these conditions survive, or boys with [[Klinefelter's syndrome]] (and hence have more than one X chromosome).

A few scholars have suggested discontinuing the use of the terms ''dominant'' and ''recessive'' when referring to X-linked inheritance, stating that the highly variable penetrance of X-linked traits in females as a result of mechanisms such as [[skewed X-inactivation]] or [[somatic mosaicism]] is difficult to reconcile with standard definitions of dominance and recessiveness.<ref name="pmid15316978">{{cite journal|vauthors=Dobyns WB, Filauro A, Tomson BN, Chan AS, Ho AW, Ting NT, Oosterwijk JC, Ober C|date=August 2004|title=Inheritance of most X-linked traits is not dominant or recessive, just X-linked|journal=American Journal of Medical Genetics. Part A|volume=129A|issue=2|pages=136–43|doi=10.1002/ajmg.a.30123|pmid=15316978}}</ref>

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==List of dominant X-linked diseases==

* [[Vitamin D]] resistant [[rickets]]: [[X-linked hypophosphatemia]]

* [[Rett syndrome]] (95% of cases are due to sporadic mutations(not inherited))

* [[Fragile-X syndrome]]

* Most cases of [[Alport syndrome]]<ref name=pmid14514738>{{cite journal | vauthors = Jais JP, Knebelmann B, Giatras I, De Marchi M, Rizzoni G, Renieri A, Weber M, Gross O, Netzer KO, Flinter F, Pirson Y, Dahan K, Wieslander J, Persson U, Tryggvason K, Martin P, Hertz JM, Schröder C, Sanak M, Carvalho MF, Saus J, Antignac C, Smeets H, Gubler MC | display-authors = 6 | title = X-linked Alport syndrome: natural history and genotype-phenotype correlations in girls and women belonging to 195 families: a "European Community Alport Syndrome Concerted Action" study | journal = Journal of the American Society of Nephrology | volume = 14 | issue = 10 | pages = 2603–10 | date = October 2003 | pmid = 14514738 | doi = 10.1097/01.ASN.0000090034.71205.74 | doi-access = free | hdl = 2078.1/40773 | hdl-access = free }}</ref>

* [[Incontinentia pigmenti]]<ref>{{cite web | url = http://dermnetnz.org/systemic/incontinentia-pigmenti.html | title = Incontinentia pigmenti | first = Vanessa | last = Ngan | name-list-style = vanc | publisher = DermNet NZ | date = 2005 }}</ref><ref>{{EMedicine|article|1114205|Incontinentia Pigmenti}}</ref>

* [[Giuffrè–Tsukahara syndrome]]<ref name=pmid20635354>{{cite journal | vauthors = Dalal AB, Sarkar A, Priya TP, Nandineni MR | title = Giuffrè-Tsukahara syndrome: Evidence for X-linked dominant inheritance and review | journal = American Journal of Medical Genetics. Part A | volume = 152A | issue = 8 | pages = 2057–60 | date = August 2010 | pmid = 20635354 | doi = 10.1002/ajmg.a.33505 }}</ref>

* [[Goltz syndrome]]

* X-linked dominant [[porphyria]]<ref name=pmid24131146>{{cite journal | vauthors = Seager MJ, Whatley SD, Anstey AV, Millard TP | title = X-linked dominant protoporphyria: a new porphyria | journal = Clinical and Experimental Dermatology | volume = 39 | issue = 1 | pages = 35–7 | date = January 2014 | pmid = 24131146 | doi = 10.1111/ced.12202 }}</ref>

* [[Aicardi Syndromesyndrome]]

== See also ==