Inheritance and Genetics of X-linked Dominant Genetic Diseases

Inheritance of X-linked Dominant Genetic Diseases:

X-linked dominant diseases are usually inherited, though rare cases of sporadic genetic disease can also occur. X-linked dominant diseases are far rarer than x-linked recessive diseases or autosomal dominant diseases. See details of inheritance patterns in article Inheritance of X-Linked Dominant Genetic Diseases.

X-linked Dominant Genetic Diseases: Inheritance and Genetics Details

Inheritance properties of X-linked Dominant Genetic Diseases:   Disease inherited from: Daughters inherit from either parent, but sons can only inherit from the mother. Also possible is sporadic disease.

  Gender bias in inheritance: Both males and females can have the disease, since both can have an X chromosome with a bad gene that dominates. However, more females have the disease than men. This is because daughters have 100% inheritance from fathers combined with 50% from mothers, whereas sons only have 50% from mothers. Statistically, there should be 3 times as many women with the disease as men.

Inheritance Patterns

Inheritance odds for X-linked Dominant Genetic Diseases:   Overall odds of inheritance: Daughters inherit from either parent, but sons can only inherit from the mother. Also possible is sporadic disease.

  Mother to son inheritance odds: 50% chance of disease because the son gets one X chromosome from the mother, and has a 50% chance of getting the bad one versus the good gene.

  Father to son inheritance odds: 0% chance of disease (because the father's sperm provides only the Y chromosome, the son's good X comes from the mother's egg).

  Mother to daughter inheritance odds: 50% chance of disease, because it depends on whether the child gets the good or bad X from the mother.

  Father to daughter inheritance odds: 100% chance of disease (because the father's sperm gives the daughter an X, and the XY father only has one X chromosome to give, i.e. the bad one).

Genetic Carriers

Genetic carriers of X-linked Dominant Genetic Diseases:   Carriers possible for disease?: No, not for dominant diseases

  Odds daughter becomes genetic carrier: 0%. Dominant diseases have no carriers.

  Odds son becomes genetic carrier: 0%. Dominant diseases have no carriers.

Inheritance Features

Inheritance features for X-linked Dominant Genetic Diseases:   Sporadic form of disease possible?: Yes, only one mutation on the X chromosome is required.

  Milder form of disease possible in females?: Yes, for some diseases. Although females cannot be carriers of the dominant disease, females have a second X chromosome, which should have a good gene that may mitigate somewhat against the dominant bad gene in the other X (i.e. perhaps the bad gene is not totally dominant).

  Inheritance from one double dominant parent: The rare case of a mother with double-dominant disease (i.e. both X chromosomes have bad genes), has a 100% chance of passing disease to a child of either gender. Only females can be double-dominant.

About inheritance and genetics:

Inheritance of X-linked Dominant Genetic Diseases refers to whether the condition is inherited from your parents or "runs" in families. The level of inheritance of a condition depends on how important genetics are to the disease. Strongly genetic diseases are usually inherited, partially genetic diseases are sometimes inherited, and non-genetic diseases are not inherited. For general information, see Introduction to Genetics.