Jump to navigation Jump to search This article is about sex-linked inheritance. For hybrid chickens with sexually differentiated hatchling color, see Sex-link. Experimental cross performed by Thomas Hunt Morgan , illustrating the X-linked inheritance of white-eyed mutation in fruit flies. In autosomal chromosomes both sexes have the same probability of existing see Fisher's principle , but since humans have many more genes on the female X chromosome than on the male Y chromosome , these are much more common than Y-linked traits. In mammals , the female is homogametic, with two X chromosomes XX , while the male is the heterogametic sex , with one X and one Y chromosome XY. Genes on the X or Y chromosome are called sex-linked.
Sex chromosomes & X-linked inheritance (article) | Khan Academy
Thus, X-linked mutations tend to be rare in women. The second reason for female rarity is that women who express the mutation must have two X chromosomes that carry the trait and they necessarily got one from their father, who would have also expressed the trait because he only had one X chromosome in the first place. If the trait lowers the probability of fathering a child or causes the father to choose to only have children with women who aren't carriers so as not to create daughters who are carriers rather than expressers and then only if no genetic screening is used then women become even less likely to express the trait. Most common[ edit ] The most common X-linked recessive disorders are: Its commonness may be explained by its relatively benign nature.
The two gametes came together during fertilization to produce a diploid individual. There is, however, one exception to this: Until now, we have only considered inheritance patterns among non-sex chromosomes, or autosomes. In addition to 22 homologous pairs of autosomes, human females have a homologous pair of X chromosomes, whereas human males have an XY chromosome pair.
URL of this page: X and Y are sex chromosomes. Dominant inheritance occurs when an abnormal gene from one parent causes disease, even though the matching gene from the other parent is normal. The abnormal gene dominates. But in recessive inheritance, both matching genes must be abnormal to cause disease.