16) A man and a woman walk into a genetic counselor’s office. The woman has a br

Question

16) A man and a woman walk into a genetic counselor’s office. The woman has a brother who has been diagnosed with hemophilia, a sex-linked condition. The man has no family history of the illness. They are considering having children. Which of the following statements are appropriate and correct things to say to this couple?

1-The chance of any given child from this couple having hemophilia is approximately 50%

2-Assuming the woman and her afflicted brother have the same mother, the chance of a male child from this couple having hemophilia is approximately 50%

3-The chance of a female child from this couple having hemophilia is approximately 50%

4-An egg donor might be a good idea, if they are open to the idea

5-A sperm donor might be a good idea, if they are open to the idea

6-The two should probably adopt, and not spread their bad genes

A. 1, 2, and 6
B. 1 and 5
C. 2 and 4
D. 1-6, all statements are correct and appropriate
E. None of 1-6 are correct and appropriate

Explanation / Answer

It is x linked disease. Let us considered a condition where X' is affected disease.

i.e XX'(women) XY(male)

now there offspring will have XX', XX, XY and X'Y

there is probability of 1/4 that child will possese same disease.

If the child is male then it have 50% chance. [ because no of boys is 2, and affected boy=1; therefore probability=1/2=50%.

simmilarly girl child have 50% chance to be affected.

So option 2 and 3 is right ans.

option 4 is also right because the donor egg is not affected, so child would be healthy.

But option 5 is wrong because XX' chromosome of wife is affected. Although the sperm is donated, the XX' chromosome is affected which may cause disease.

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