Sex-linked traits are characteristics or traits that are influenced by genes carried on the sex chromosomes. In humans, the term often refers to traits or disorders influenced by genes on the X chromosome, as it contains many more genes than the smaller Y chromosome. Males, who have only a single copy of the X chromosome, are more likely to be affected by a sex-linked disorder than females, who have two copies. In females, the presence of a second, non-mutated copy may cause different, milder, or no symptoms of a sex-linked disorder.
Some of the more familiar sex-linked traits are hemophilia, red-green color blindness, congenital night blindness, some high blood pressure genes, Duchenne muscular dystrophy, and Fragile X syndrome. Sex linkage applies to genes that are located on the sex chromosomes, and these genes are considered sex-linked because their expression and inheritance patterns differ between males and females. X-linked genes have distinctive inheritance patterns because they are present in different numbers in females (XX) and males (XY) . X-linked human genetic disorders are much more common in males than in females due to the X-linked inheritance pattern.
In summary, sex-linked traits are traits controlled by their presence on the X or Y chromosome, and they have different inheritance patterns between males and females.
