(genetics) That which is associated with the X chromosome
The term X-linked is defined as that which is associated with the X chromosome. The X chromosome is a sex chromosome in mammals that typically occurs in two in females and one in males. In humans, the X chromosome bears about 800 protein-coding genes compared with the Y chromosome that bears only about 70. The genes located in the X chromosome are referred to as X-linked genes.
A female offspring inherits one X chromosome from her mother and the other from her paternal grandmother. A male offspring, in turn, inherits his single X chromosome from his mother. Inheritance involving the gene(s) on the X chromosome is called X-linked inheritance. A trait of particular medical importance, such as genetic disorder, due to a deleterious gene located on the X chromosome is referred to as an X-linked trait. It may be dominant or recessive. Examples of disorders that are X-linked dominant include Alport's syndrome, idiopathic hypoparathyroidism, Rett syndrome, and fragile X syndrome. Some of the X-linked recessive disorders are Hunter syndrome, haemophilia A and B, color blindness, and Wiskott-Aldrich syndrome.