X-linked+dominant

=X-linked dominant=

**X-linked dominance** is a pattern of inheritance involving a dominant allele that is carried on an X chromosome. X-linked dominant diseases include Charcot-Marie Tooth Disease (CMT).

The pedigree below shows a typical pattern of inheritance for an X-linked dominant disease:



There are many hallmarks of X-linked dominant diseases, notably:


 * **More females are affected than males**, due to the presence of an additional X chromosome in females, which increases the probability of inheriting the disease allele.


 * **An affected mother's offspring, whether male or female, has a 50% chance of being affected**, depending on which maternal X chromosome is inherited


 * **An affected father will affect all of his daughters but none of his sons**, since the daughter can only inherit the affected paternal X chromosome and the son can only inherit his father's Y chromosome


 * **There is no male-to-male transmission **, since only the Y chromosome is transmitted down the male line.


 * **Males are usually more severely affected than females**, because there is no compensation from a harmless allele as there is in females (males are hemizygous for X chromosome genes)