Question

Which of the following is true about children whose mother has a normal phenotype, but their father has an X-linked dominant trait?

1) 50
2) All the sons will be affected, but none of the daughters
3) All of the daughters will be affected, but none of the sons
4) 75

Answer 1

Children with a mother who has a normal phenotype and a father with an X-linked dominant trait will result in all daughters being affected by the trait, while none of the sons will be affected.

Step-by-step explanation:

When considering a situation where the mother has a normal phenotype, and the father has an X-linked dominant trait, it is critical to understand how X-linked traits are inherited.

Since the father has an X-linked dominant trait, he will pass it to all his daughters because daughters receive one X chromosome from their father and one from their mother. However, sons receive the Y chromosome from their father and an X chromosome from their mother, meaning they inherit the trait from their father only if it is also present on the X chromosome they receive from their mother. Since the mother has a normal phenotype, she does not carry the dominant X-linked trait, and therefore none of the sons will be affected. So the correct statement is that all of the daughters will be affected, but none of the sons.

Answer 2

In the case of an X-linked dominant trait with a normal mother and an affected father, all daughters will inherit the affected X chromosome and thus express the dominant trait, while sons will not be affected.

Step-by-step explanation:

The question asks about the inheritance pattern of an X-linked dominant trait where the mother has a normal phenotype and the father has the X-linked dominant trait. In this case, all daughters and none of the sons would receive the affected X chromosome. Since males inherit their X chromosome from their mother and a Y chromosome from their father, they would not inherit the affected X chromosome if the mother's phenotype is normal.

Daughters, on the other hand, would inherit one X chromosome from their mother and the affected X chromosome from their father, leading to the expression of the dominant trait.

Therefore, the correct option in this scenario is that all of the daughters will be affected, but none of the sons. The mentioned correct option in final answer is that all daughters will be affected by the X-linked dominant trait passed on by their father.