As the X chromosome is one of the sex chromosomes (the other being the Y chromosome), X-linked inheritance is determined by the sex of the parent carrying a specific gene and can often seem complex. This is due to the fact that, typically, females have two copies of the X-chromosome, while males have only one copy. The difference between<unk>  and recessive inheritance patterns also plays a role in determining the chances of a child inheriting an X-linked disorder from their parentage. Males can only get an X chromosome from their mother whilst females get an X chromosome from both parents. As a result, females tend to show higher prevalence of X-linked<unk>  disorders because they have more of a chance to inherit a faulty X chromosome. Inheritance In<unk> , when the mother alone is the carrier of a mutated, or defective gene associated with a disease or disorder; she herself will have the disorder. Her children will inherit the disorder as follows: * Of her daughters and sons: 50% will have the disorder, 50% will be completely unaffected. Children of either sex have an even chance of receiving either of their mother's two X chromosomes, one of which contains the defective gene in question. When the father alone is the carrier of a defective gene associated with a disease or disorder, he too will have the disorder. His children will inherit the disorder as follows: * Of his daughters: 100% will have the disorder, since all of his daughters will receive one copy of his single X chromosome. * Of his sons: none will have the disorder; sons do not receive an X chromosome from their father. If both parents were carriers of a defective gene associated with a disease or disorder, they would both have the disorder. Their children would inherit the disorder as follows: * Of their daughters: 100% will have the disorder, since all of the daughters will receive a copy of their father's X chromosome. * Of the sons: 50% will have the disorder, 50% will be completely unaffected. Sons have an equal chance of receiving either of their mother's X chromosomes. In such a case, where both parents carry and thus are affected by an X-linked<unk>  disorder, the chance of a daughter receiving two copies of the X chromosome with the defective gene is 50%, since daughters receive one copy of the X chromosome from both parents. Were this to occur with an X-linked<unk>  disorder, that daughter would likely experience a more severe form. Some X-linked<unk>  conditions such as Aicardi syndrome are fatal to boys; therefore only girls with these conditions survive, or boys with Klinefelter's syndrome (and hence have more than one X chromosome). A few scholars have suggested discontinuing the use of the terms<unk>  and recessive when referring to X-linked inheritance, stating that the highly variable penetrance of X-linked traits in females as a result of mechanisms such as skewed X-inactivation or somatic mosaicism is difficult to reconcile with standard definitions of<unk> e and recessiveness.
X-linked dominant inheritance
X-linked recessive inheritance
Extranuclear inheritance
Non-Mendelian inheritance
Structural inheritance
Sex linkage
Thrifty phenotype
Chromosomal fragile site