X-Linked Dominant Genes

Dominant X-linked genes are always expressed in both the sexes just as in autosomal traits. One dose of X-linked dominant allele produces its effects in males as well as females. The hemizygous male transmits the gene to all its daughters but none to his sons. There is no father to son transmission. The heterozygous females transmit the trait to half their children, irrespective of lhcir sex. On the other hand, females homozygous for the dominanl allele produce all affectcd children. For example, a form of vitamin D-resistant rickets is inhcrited as an X-linked dominant
trait (Figure shown below).