(genetics) Inheritance for genes on the X chromosome
Sex chromosomes are not only relevant for sex determination. They carry genes that are associated with other traits. Thus, it is not uncommon to see certain traits manifesting as sex-linked. In humans and other animals, there are two types of sex-linked inheritance: (1) X-linked inheritance and (2) Y-linked inheritance.
X-linked inheritance is a form of inheritance for the genes located on the X chromosome. Based on the allosomes present, human and other mammalian females have two X chromosomes whereas males have one X chromosome and one Y chromosome. X chromosome carries more genes than the Y chromosome. Thus, compared with Y-linked genes, there are more X-linked genes inherited. Some X-linked traits in humans are color blindness, muscular dystrophy, hemophilia, congenital deafness, spinal ataxia, ocular albinism, brown teeth, congenital cataract, retinitis pigmentosa, diabetes insipidus, etc.
The X-linked inheritance for a particular gene in females may either be homozygous or heterozygous. A heterozygous female for a particular X-linked recessive gene is a carrier of the recessive allele. In males, the X-linked inheritance for an X-linked gene is described as hemizygous since there is only one X chromosome involved.