X chromosome
The X chromosome is one of the two sex chromosomes in mammals.[1] 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 egg always carries a single X, while sperms carry either an X or a Y. That is how sex is determined in humans,[2] and in most other mammals. 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 cats.
X Chromosome Media
The number of possible ancestors on the X chromosome inheritance line at a given ancestral generation follows the Fibonacci sequence. (After Hutchison, L. "Growing the Family Tree: The Power of DNA in Reconstructing Family Relationships".)
Nucleus of a female amniotic fluid cell. Top: Both X-chromosome territories are detected by FISH.
Human chromosome X. G-banding ideogram in resolution 850 bphs.
Ideograms of G-band pattern of human X chromosome in three different resolutions (400, 550 and 850 bphs, bands per haploid set). Different resolutions are corresponding to different band patterns observed through mitotic phase (about relation between banding resolution and mitotic phase, see, for example, Fig.3 in
Human chromosome X. G-banding ideogram in resolution 850 bphs.
Related pages
References
- ↑ See sex determination for a fuller account.
- ↑ Bainbridge, David A. 2003. The X in sex: how the X chromosome controls our lives. Harvard.