Question

Consider a colour blind woman who has married a normal man (without colour blindness). They have one son and one daughter. Which of the following statements about their children is/are true?

• A. Both suffer from colour blindness.
• B. Boy suffers from colour blindness, while girl has normal vision.
• C. Boy has normal vision, while the girl has colour blindness.
• D. Not enough information to decide.

Answer 1

The correct option is B

Boy suffers from colour blindness, while girl has normal vision.

If the mother is colour blind, it means that both the X chromosomes have the gene for haemophilia. Therefore, when the X chromosome passes on to the boy, he suffers from haemophilia. The daughter cannot suffer from it, since the father does not have it. The daughter will therefore be a carrier.