referring to a pattern of inheritance characteristic of genes located on one type of sex chromosome (for example X) and not found on the other type (for example Y); in mammals, in almost all cases, the gene controlling the trait is on the X chromosome so this pattern is often called X-linked. In X-linked inheritance, females show the dominant trait unless they are homozygous recessive, whereas males express whichever allele, dominant or recessive, that is found on their single X chromosome