sexlinked

Sex-linked is a term used in genetics to describe genes that are located on the sex chromosomes, most often the X chromosome in humans. In species with XY sex determination, the main distinctions are X-linked and Y-linked genes. Because females have two X chromosomes and males have one X and one Y, patterns of inheritance differ from autosomal (non-sex) genes. Y-linked traits are passed from father to son and are relatively rare, while X-linked genes can affect both sexes but show characteristic patterns of transmission.

X-linked traits include recessive and dominant forms. X-linked recessive conditions, such as color blindness, hemophilia A, and Duchenne muscular dystrophy, are more common in males because they have only one X chromosome; a single mutated allele on that X will often produce the trait. Females can be carriers if they have one copy of the mutated allele, typically remaining unaffected or mildly affected. X-linked dominant traits can affect both sexes, but affected fathers pass the trait to all daughters and none of their sons.

X-inactivation, or Lyonization, in females can lead to mosaic expression of X-linked genes, contributing to variable manifests of some conditions and to patterns like calico coat coloration in cats. Y-linked genes, by contrast, are fewer in number and are transmitted from father to son, often relating to male-specific development and fertility. In genetics and counseling, the sex-linked pattern informs risk assessment for offspring.