In Barbados, a mother who is a carrier for haemophilia has children with a man who does not have the disease. What is the probability that their son will have haemophilia?

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Question

In Barbados, a mother who is a carrier for haemophilia has children with a man who does not have the disease. What is the probability that their son will have haemophilia?

Accepted Answer

50% — Award 1 mark for correct probability. The mother (XHXh) can pass either the normal X (XH) or the affected X (Xh) to her sons. Sons inherit their only X chromosome from their mother, so there is a 50% chance of inheriting Xh and having haemophilia. A is incorrect — there is a possibility of inheritance. B is incorrect — this would be the probability for all children, not specifically sons. D is incorrect — not all sons will be affected.

Answer

25%

Answer

100%

Answer

0%

Answer

50%

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