gonosomal

Gonosomal refers to genes located on the sex chromosomes, the gonosomes, and to inheritance patterns associated with those chromosomes. In many organisms, including humans, the gonosomes are the X and Y chromosomes; in other groups, such as birds and some insects, the sex-determination system may involve different sex chromosomes like Z and W. Gonosomal genes are distinguished from autosomal genes, which lie on the non-sex chromosomes and are generally inherited independently of sex.

In XY species, X-linked genes reside on the X chromosome. Males have only one copy of X-linked genes and are therefore hemizygous for them. This underpins several classic X-linked inheritance patterns: X-linked recessive traits often appear more in males, and affected fathers pass the allele to all daughters but not to sons, while carrier mothers can transmit the allele to half of their offspring. Y-linked genes, located on the Y chromosome, are passed from father to son and typically affect traits found only in males.

Dosage compensation mechanisms adjust expression of sex-linked genes to balance sexes; in mammals this involves X-chromosome inactivation in females. Other taxa show different strategies; for example, birds have ZW females and dosage-regulation patterns distinct from mammals. Some gonosomal genes escape inactivation or are imprinted, contributing to sex differences in trait expression and disease susceptibility.

The study of gonosomal inheritance informs genetic counseling, research on sex-specific diseases, and evolutionary biology, illustrating how chromosome structure and sex determination influence heredity.