What is a characteristic of X-linked recessive disorders?

A characteristic of X-linked recessive disorders is that females can only be carriers if affected fathers are present. In X-linked recessive inheritance, males possess one X chromosome and one Y chromosome, while females have two X chromosomes. If a father is affected by an X-linked recessive disorder, he will pass his Y chromosome to his sons, meaning his sons cannot inherit the disorder from him. However, all daughters will inherit their father's affected X chromosome, making them carriers of the disorder.

Since females have two X chromosomes, they can be carriers if one X chromosome carries the recessive allele while the other does not. Consequently, a daughter from an affected father who inherits a normal X chromosome from the mother will be a carrier. In summary, affected fathers directly influence whether daughters become carriers, solidifying that females can only be carriers when affected fathers are present.