The X and Y chromosomes differ in shape, size, and genetic makeup. The X chromosome refers to large chromosomes with a large number of genes. The Y chromosome is smaller and contains fewer genes.
Many of the genes located on the sex chromosomes determine traits that are not related to gender development. But the genes are on the sex chromosomes, and the traits are sex-linked.
Sex-linked inheritance has a number of features. Since most genes localized on the X chromosome do not have their alleles on the Y chromosome, the heterogametic sex (XY) displays all genes contained in a single X chromosome.
A person has a heterogametic male sex. Men have only one X chromosome, therefore, regardless of the dominance or recessiveness of the gene located in it, it will manifest itself. A number of diseases are determined by a recessive gene located on the X chromosome. Such diseases are more common in men than in women.
Sex-linked pathologies such as hemophilia (incoagulability of blood) and color blindness (impaired color perception) are inherited. These diseases are determined by recessive genes. In women, hemophilia and color blindness are rare, and in men more often.
Fathers never pass their X chromosome to sons, but always to daughters. The daughter inherits the disease only if both parents have recessive genes (the father is sick and the mother is sick or the carrier). The son inherits the disease from the mother if she is sick, and can inherit with a 50% probability if she is healthy, but carries the gene that determines the pathology.