What is X chromosome?
[[File:Calico cat - Phoebe.jpg|thumb|right|alt=Calico cat (Felis silvestris catus)| Inactivation of one of the X chromosomes is responsible for the patterns on [[calico cat]]s]] The '''X chromosome''' is one of the two [[sex chromosome]]s in [[mammals]].<ref>See [[sex determination]] for a fuller account.</ref> They decide the sex ([[gender]]) of an individual. The other sex chromosome is the [[Y chromosome]]. Females have two X chromosomes, males have one X and one Y. An [[Ovum|egg]] always carries a single X, while [[sperm]]s carry either an X or a Y. That is how sex is determined in humans,<ref>Bainbridge, David A. 2003. ''The X in sex: how the X chromosome controls our lives''. Harvard.</ref> and in most other [[mammal]]s. Although females have two X chromosomes, each cell can only have one X chromosome active. During early development, a process called [[X-inactivation]] occurs. In each cell one of the X chromosomes randomly deactivates. This causes different parts of the body to have different X-linked genes, and is responsible for the black and orange coloration of [[calico cat]]s. == Related pages == *[[Sex determination]] *[[Karyotype]] *[[Chromosome]] == References == {{Reflist}} [[Category:Biological reproduction]] [[Category:Chromosomes]] {{biology-stub}}