Editing Barr body (section)

=== Barr Body Analysis in Genetic Disorder Diagnosis ===
Barr bodies analysis is a rapid screening tool that can be used for preliminary identification of potential X chromosome [[aneuploidy]]. Results can be available within an hour, compared to [[karyotyping]] that typically takes 1-2 weeks.<ref name=":3">{{Cite journal |last1=Kamischke |first1=Axel |last2=Baumgardt |first2=Arthur |last3=Horst |first3=Jürgen |last4=Nieschlag |first4=Eberhard |date=2003 |title=Clinical and Diagnostic Features of Patients With Suspected Klinefelter Syndrome |url=https://onlinelibrary.wiley.com/doi/full/10.1002/j.1939-4640.2003.tb02638.x |journal=Journal of Andrology |language=en |volume=24 |issue=1 |pages=41–48 |doi=10.1002/j.1939-4640.2003.tb02638.x |issn=1939-4640}}</ref> Although Barr body analysis cannot provide a definitive diagnosis, as karyotyping is required for confirmation, diagnostic accuracy is high.<ref name=":3" /> The conditions that can be identified include:

==== Turner Syndrome (45,X) ====
[[Turner syndrome]] is caused by the complete or partial absence of a second X chromosome in phenotypic females.<ref name=":4">{{Citation |last1=Shankar Kikkeri |first1=Nidhi |title=Turner Syndrome |date=2025 |work=StatPearls |url=https://www.ncbi.nlm.nih.gov/books/NBK554621/ |access-date=2025-04-03 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=32119508 |last2=Nagalli |first2=Shivaraj}}</ref> Approximately 50% of cases involve monosomy X, resulting in a 45,X karyotype that lacks a Barr body due to the presence of only one X chromosome.<ref name=":4" /> In cases involving partial deletions or structural abnormalities of the second X chromosome, Barr bodies are typically also absent, as a fully functional second copy of the X chromosome is required for X inactivation and subsequent Barr body formation.<ref name=":4" />

==== Klinefelter Syndrome (47,XXY) ====
[[Klinefelter Syndrome]] is an aneuploidy in phenotypic males, characterized presence of two or more X chromosomes.<ref name=":12">{{Citation |last1=Los |first1=Evan |title=Klinefelter Syndrome |date=2025 |work=StatPearls |url=https://www.ncbi.nlm.nih.gov/books/NBK482314/ |access-date=2025-04-03 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=29493939 |last2=Leslie |first2=Stephen W. |last3=Ford |first3=George A.}}</ref> The most common karyotype is 47,XXY but other variations (48,XXXY, and 49,XXXXY) have been reported.<ref name=":12" /> Unlike typical 46,XY males, individuals with Klinefelter syndrome undergo X chromosome inactivation, with the additional X chromosome forming a Barr body. In cases involving multiple extra X chromosomes, more than one Barr body may be observed.<ref name=":12" />

==== Triple X Syndrome (47,XXX) ====
[[Trisomy X|Triple X Syndrome]] is an aneuploidy of the X chromosome in phenotypic females, resulting in an additional X chromosome.<ref name=":5">{{Cite journal |last1=Otter |first1=Maarten |last2=Schrander-Stumpel |first2=Constance TRM |last3=Curfs |first3=Leopold MG |date=March 2010 |title=Triple X syndrome: a review of the literature |journal=European Journal of Human Genetics |language=en |volume=18 |issue=3 |pages=265–271 |doi=10.1038/ejhg.2009.109 |pmid=19568271 |pmc=2987225 |issn=1476-5438}}</ref> Individuals with this condition typically have two Barr bodies per somatic cell, as two of the three X chromosomes undergo inactivation.<ref name=":5" />