Chromosome X: General Features

Abstract

The X chromosome is the larger of the pair of chromosomes that determine sex in mammals. It is present in two copies in females, while one copy pairs with the sex determining Y chromosome in males.

Keywords: X chromosome

Figure 1.

Hemophilia pedigree of Queen Victoria's offspring. Females are represented by circles and males by squares. Affected individuals are represented by filled squares. Carrier females are represented by a smaller filled circle. Note how the disease is apparent in males of only every second generation, the classic skipping of generations that is associated with X‐linked recessive disease.

Figure 2.

Metaphase chromosome spread from a patient with fragile X. Note the constriction on the long arm of the X chromosome (indicated by the arrow and enlarged in inset). (Picture courtesy Professor C. M. Disteche, Department of Pathology, University of Washington, Seattle, WA, USA.)

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Further Reading

Graves JAM (1995) The origin and function of the mammalian Y chromosome and Y‐borne genes – an evolving understanding. BioEssays 17: 311–320.

Graves JAM and Delbridge ML (2001) The X – a smart and sexy chromosome. BioEssays 23: 1091–1094.

Lubs H, Chiurazzi P, Arena J, Tranebjaerg L and Neri G (1999) XLMR genes: update 1998. American Journal of Medical Genetics 83: 237–247.

Nathans J (1999) The evolution and physiology of human color vision: insights from molecular genetic studies of visual pigments. Neuron 24: 299–312.

Ohno S (1967) Sex Chromosomes and sex Linked Genes Berlin: Springer.

Web Links

National Hemophilia Foundation http://www.hemophilia.org/

IRSA: International Rett Syndrome Association http://www.rettsyndrome.org/

The National Fragile X Foundation http://www.fragileX.org/

Androgen receptor (dihydrotestosterone receptor; testicular feminization; spinal and bulbar muscular atrophy; Kennedy disease) (AR); Locus ID: 367 LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=367

Coagulation factor VIII, procoagulant component (hemophilia A) (F8); Locus ID: 2157 LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=2157

Fragile X mental retardation 1 (FMR1); Locus ID: 2332 LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=2332

Methyl CpG binding protein 2 (Rett syndrome) (MECP2); Locus ID: 4204 LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=4204

Sex determining region Y (SRY); Locus ID: 6736 LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=6736

X (inactive)‐specific transcript (XIST); Locus ID: 7503 LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=7503

Androgen receptor (dihydrotestosterone receptor; testicular feminization; spinal and bulbar muscular atrophy; Kennedy disease) (AR); MIM number: 313700 OMIM: http://www.ncbi.nlm.nih.gov/htbin‐post/Omim/dispmim?313700

Coagulation factor VIII, procoagulant component (hemophilia A) (F8); MIM number: 306700 OMIM: http://www.ncbi.nlm.nih.gov/htbin‐post/Omim/dispmim?306700

Fragile X mental retardation 1 (FMR1); MIM number: 309550 OMIM: http://www.ncbi.nlm.nih.gov/htbin‐post/Omim/dispmim?309550

Methyl CpG binding protein 2 (Rett syndrome) (MECP2); MIM number: 300005 OMIM: http://www.ncbi.nlm.nih.gov/htbin‐post/Omim/dispmim?300005

Sex determining region Y (SRY); MIM number: 480000 OMIM: http://www.ncbi.nlm.nih.gov/htbin‐post/Omim/dispmim?480000

X (inactive)‐specific transcript (XIST); MIM number: 314670 OMIM: http://www.ncbi.nlm.nih.gov/htbin‐post/Omim/dispmim?314670

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How to Cite close
Wakefield, Matthew J, and Graves, Jennifer AM(Jan 2006) Chromosome X: General Features. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0005794]