Males can only get an X chromosome from their mother whilst females get an X chromosome from both parents. The difference between dominant and recessive inheritance patterns also plays a role in determining the chances of a child inheriting an X-linked disorder from their parentage. This is due to the fact that, typically, females have two copies of the X-chromosome, while males have only one copy. Some X-linked dominant conditions are embryonic lethal in males, making them appear to only occur in females.Īs 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.
When the son is affected, the mother will always be affected. However, if the mother is also affected then sons will have a chance of being affected, depending on whether a dominant or recessive X chromosome is passed on. All fathers that are affected by an X-linked dominant disorder will have affected daughters but not affected sons. The exact pattern of inheritance varies, depending on whether the father or the mother has the trait of interest. X-linked dominant traits do not necessarily affect males more than females (unlike X-linked recessive traits).
In this case, someone who expresses an X-linked dominant allele will exhibit the disorder and be considered affected. In medicine, X-linked dominant inheritance indicates that a gene responsible for a genetic disorder is located on the X chromosome, and only one copy of the allele is sufficient to cause the disorder when inherited from a parent who has the disorder. As an inheritance pattern, it is less common than the X-linked recessive type. X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.