A couple has a normal vision, although both of their fathers are red-green colour-blind. What is the probability in the following cases?

i. A normal son
ii. A carrier daughter
iii. A colour-blind son
iv. A colour blind daughter

Question

TestHub · Accepted Answer

Mother is a carrier (because her father is colour-blind) and father is normal. Thus, their genotype X c X and XY respectively. So the probability that their first child will be A normal son =1/4, A carrier daughter =1/4. A colour-blind son =1/4, A colour-blind daughter =0. (Both husband and wife have normal vision through their fathers were colour-blind, the probability of their daughter becoming colour-blind is 0%. The chances of a daughter becoming colour blind arise only when the father is also colour-blind.)

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