Sex linked traits are only found on the X chromosome. If the gene is recessive, then males only need one such recessive gene to have a sex-linked trait rather than the customary two recessive genes for traits that are not sex-linked. This is why males exhibit some traits more frequently than females.
XX, Xx, xx, XY, and xY are possible genotypes.
Hemophilia is X-linked recessive. Symptoms are excessive bleeding due to lack of blood clotting proteins. People can live a nearly normal life span now due to medicine.
X- inactivation occurs in females. They carry twice as much genetic material, so x- inactivation balances it out by randomly inactivating an X chromosome in a cell. A barr body is the inactivated X.
