X linked recessive inheritance

In X linked recessive conditions males are affected because
they have only a single copy of genes carried by the
X chromosome (hemizygosity), but the disorder can be
transmitted through healthy female carriers. A female carrier
of an X linked recessive disorder will transmit the condition to
half her sons, and half her daughters will be carriers. An
unaffected male does not transmit the disorder. An affected
male will transmit the mutant gene to all his daughters (who
must inherit his X chromosome), but to none of his sons (who
must inherit his Y chromosome). This absence of male to male
transmission is a hallmark of X linked inheritance. Many X
linked recessive disorders are severe or lethal during early life,
however, so that the affected males do not reproduce.