A man and a woman walk into a genetic counselor’s office. The man’s brother has

Question

A man and a woman walk into a genetic counselor’s office. The man’s brother has been diagnosed with hemophilia, an X linked genetic illness caused by a rare, recessive allele. The woman has no family history of the illness. They want to know if they are at risk for having a child with the illness. Which of the following statements should the counselor say?

Their risk is rather minimal, since the man has no chance of being a “carrier” for the illness.

There is a very small risk that the woman is a carrier for the illness, but this is improbable since hemophilia has never been observed in male members of her family.

The man has a fifty percent chance of being a carrier for the illness.

Half the male children this couple produces will be affected by the illness.

The situation would be much different if hemophilia were present on the woman’s side of the family.

Explanation / Answer

A). Their risk is rather minimal, since the man has no chance of being a “carrier” for the illness.

B). There is a very small risk that the woman is a carrier for the illness, but this is improbable since hemophilia has never been observed in male members of her family.

E). The situation would be much different if hemophilia were present on the woman’s side of the family.

In sex linked or X-linked diseases, the defective allele is present in X-chromosome. X- linked diseases could be developed in females only when they inherit two X-linked recessive alleles, one from the mother and another from the father. Whereas in males, presence of only one defective allele will result in expression of disease phenotype. Haemophilia is an example of X-linked disease in which females act as carriers and males are generally affected (males never act as only carriers, they can transmit the disease only if they are affected).

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.