X-Linked Inheritance

X-linked conditions are caused by mutations in genes on the X chromosome. X-linked inheritance functions differently in males and females.


There are conditions caused by mutations in genes on the X chromosome. These are called x-linked conditions.**

Females have two copies of the X chromosome, one from mom and one from dad. Therefore, if females have a mutation in a gene on one X chromosome, they are usually unaffected because the second gene copy on the other X chromosome is enough to support typical growth and development.

On the other hand, males have one X and one Y chromosome. The X comes from mom, and the Y comes from dad. This means that if a male has a mutation in a gene on the X chromosome, he will almost always show symptoms of the related condition. There is no second copy of the X chromosome to balance it out.

You might be able to recognize this type of inheritance in your family history. X-linked conditions are typically present only in males, and they are never passed from a father to his son. Just like with dominant inheritance, a person with an X-linked condition could also have a new, or de novo, mutation, and be the first in the family to show symptoms.

In an X-linked recessive inheritance pattern, if a woman with a mutation on the X chromosome has a male child, there is a 50% (or 1 in 2) chance that he will be affected. If she has a female child, there is a 50% (or 1 in 2) chance that she will be a carrier.

These numbers may be different in X-linked dominant conditions.

This topic can be complex, but your genetic healthcare provider will discuss this in more detail if it applies to you and your family.