In genetic inheritance, what does a father with affected daughters imply in an X-linked trait?

When a father has affected daughters in the context of genetic inheritance, it suggests that the trait in question is likely X-linked dominant. This is because daughters inherit one of their X chromosomes from their father and one from their mother. If a father is affected by an X-linked dominant trait, he can pass his affected X chromosome to all of his daughters. As a result, all daughters of an affected father will express the trait, making it evident that the trait is associated with the X chromosome and is dominant in expression.

In contrast, an autosomal recessive condition would require both parents to carry the recessive allele for the daughters to be affected. If the mother does not carry the recessive gene, the daughters cannot be affected. Y-linked traits would not be relevant as only sons inherit the Y chromosome from their father, not daughters. Autosomal dominant traits could be possible if both parents contribute a dominant allele, but in this specific scenario, the father’s affected status strongly indicates it must be X-linked dominant since he directly transmits that trait to his daughters.