Question

4. Hemophilia is an inheritable genetic disorder that prohibits the proper formation of blood clots. The recessive gene that causes hemophilia is located on the X-chromosome. Given this information, which of the following statements is true?

a. In order for a male offspring to be a hemophiliac, his mother must be a hemophiliac.
b. In order for a female offspring to be a hemophiliac, her father must be a hemophiliac.
c. In order for a male offspring to be a hemophiliac, his father must be a hemophiliac.
d. In order for a female offspring to be a hemophiliac, her mother must be a hemophiliac.

Answer 1

b. In order for a female offspring to be a hemophiliac, her father must be a hemophiliac.

Step-by-step explanation:

Hemophilia is an X linked recessive disorder in which blood does not clot easily and hence abnormal bleeding occurs.

In order for a female child to be hemophiliac her father must be diseased whereas her mother must be either hemophiliac or a carrier of this disease. In case, father does not have hemophilia there is no way through which the female child could be develop hemophilia. The cross is shown as under:

In case of diseased mother (homozygous) & normal father :

Mother Father

Parents XaXa XY

F1 XaX XaY XaX XaY

Here, Xa represents diseased allele while X represents normal allele.

So, it is clear from the above mentioned cross that even though mother has both the diseased alleles yet the female child has not acquired the disorder because the father is normal. So, the father must be diseased then only female child will inherit the disease otherwise the disease will get masked.

Answer 2

option b is right that  In order for a female offspring to be a hemophiliac, her father must be a hemophiliac.