X-linked recessive inheritance: Difference between revisions

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

[[File:X-linked recessive (2).svg|thumb|right|upright=1.75|X-linked recessive inheritance]]

'''X-linked recessive inheritance''' is a mode of [[Mendelian inheritance|inheritance]] in which a [[mutation]] in a [[gene]] on the [[X chromosome]] causes the [[phenotype]] to be always expressed in males (who are necessarily [[hemizygous]] for the gene mutation because they have one X and one [[Y chromosome]]) and in females who are homozygous for the gene mutation (see [[zygosity]]). Females with one copy of the mutated gene are carriers.

X-linked inheritance means that the gene causing the trait or the disorder is located on the X chromosome. Females have two X chromosomes while males have one X and one [[Y chromosome]]. Carrier females who have only one copy of the mutation do not usually express the phenotype, although differences in [[X-chromosome inactivation]] (known as [[skewed X-inactivation]]) can lead to varying degrees of clinical expression in carrier females, since some cells will express one X [[allele]] and some will express the other. The current estimate of sequenced X-linked genes is 499, and the total, including vaguely defined traits, is 983.<ref>{{cite web|url=https://www.ncbi.nlm.nih.gov/Omim/mimstats.html|title=OMIM X-linked Genes|website=nih.gov|access-date=3 May 2018|url-status=livedead|archive-url=https://web.archive.org/web/20160307090758/http://www.ncbi.nlm.nih.gov/Omim/mimstats.html|archive-date=7 March 2016}}</ref>

== Patterns of inheritance ==

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===Most common===

The most common X-linked recessive disorders are:<ref name=gpnotebook>[http://www.gpnotebook.co.uk/simplepage.cfm?ID=-1341784030 GP Notebook - X-linked recessive disorders] {{webarchive|url=https://web.archive.org/web/20110613144555/http://www.gpnotebook.co.uk/simplepage.cfm?ID=-1341784030 |date=2011-06-13 }} Retrieved on 5 Mars, 2009</ref>

* [[Red–green color blindness]], also known as daltonism,<ref>{{cite web|url=https://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=303800|title=OMIM Color Blindness, Deutan Series; CBD|website=nih.gov|access-date=3 May 2018|url-status=livedead|archive-url=https://web.archive.org/web/20090929025156/http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=303800|archive-date=29 September 2009}}</ref> which affects roughly 7% to 10% of men and 0.49% to 1% of women. Its relative benignity may explain its commonness.

* [[Hemophilia A]], a [[coagulation|blood clotting]] disorder caused by a [[mutation]] of the [[Factor VIII]] [[gene]] and leading to a deficiency of Factor VIII. It was once thought to be the "royal disease" found in the descendants of Queen Victoria. This is now known to have been Hemophilia B (see below).<ref>{{cite web|author= Michael Price|title= Case Closed: Famous Royals Suffered From Hemophilia|url= https://www.science.org/content/article/case-closed-famous-royals-suffered-hemophilia|work= ScienceNOW Daily News|publisher= AAAS|date= 8 October 2009|access-date= 9 October 2009|url-status= live|archive-url= https://web.archive.org/web/20131020190735/http://news.sciencemag.org/biology/2009/10/case-closed-famous-royals-suffered-hemophilia|archive-date= 20 October 2013}}</ref><ref>{{cite journal |last1=Rogaev |first1=Evgeny I. |last2=Grigorenko |first2=Anastasia P. |last3=Faskhutdinova |first3=Gulnaz |last4=Kittler |first4=Ellen L. W. |last5=Moliaka |first5=Yuri K. |year=2009 |title=Genotype Analysis Identifies the Cause of the 'Royal Disease' |journal=Science |volume=326 |issue=5954 |pages=817 |bibcode=2009Sci...326..817R |doi=10.1126/science.1180660 |pmid=19815722|s2cid=206522975 |doi-access=free }}</ref>

* [[Hemophilia B]], also known as Christmas disease,<ref>[http://www.hemophilia.org/NHFWeb/MainPgs/MainNHF.aspx?menuid=181&contentid=46&rptname=bleeding "Hemophilia B".] {{webarchive|url=https://web.archive.org/web/20071201092338/http://www.hemophilia.org/NHFWeb/MainPgs/MainNHF.aspx?menuid=181&contentid=46&rptname=bleeding |date=2007-12-01 }} National Hemophilia Foundation.</ref> a [[coagulation|blood clotting]] disorder caused by a [[mutation]] of the [[Factor IX]] [[gene]] and leading to a deficiency of Factor IX. It is rarer than [[hemophilia A]]. As noted above, it was [[Haemophilia in European royalty|common]] among the descendants of Queen Victoria.

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[Female X-linked disorders]

* [https://www.nlm.nihmedlineplus.gov/medlineplus/ency/article/002051.htm Sex-linked recessive: MedlinePlus Medical Encyclopedia]

[[Category:Genetics]]