A normal-visioned man whose father was colour blind, marries a woman whose father was also colour blind. They have their first child as a daughter. What are the chances that this child would be colour blind?

Question

Accepted Answer

50%. Colour blindness is typically X-linked recessive. The man is normal but his father was colour blind, so he must have received a normal X from his mother and gives a normal X to all daughters; the woman, whose father was colour blind, is an obligate carrier and can pass the mutant X half the time. A daughter is colour blind only if she gets the mutant X from both parents, so the chance is 50% for this child being a daughter.

A normal-visioned man whose father was colour blind, marries a woman whose father was also colour blind. They have their first child as a daughter. What are the chances that this child would be colour blind?

Solution

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