A husband and wife have normal vision, although both of their fathers are red-green colour blind, which is inherited as an x-linked recessive trait. What is the probability that their first child will be? i. A normal son ii. A carrier daughter iii. A colour-blind son iv. A colour-blind daughter

Question

A husband and wife have normal vision, although both of their fathers are red-green colour blind, which is inherited as an x-linked recessive trait. What is the probability that their first child will be? i. A normal son ii. A carrier daughter iii. A colour-blind son iv. A colour-blind daughter, i = 1 4 , i i = 1 4 , i i i = 1 4 , i v = 1 4, i = 1 4 , i i = 1 4 , i i i = 1 4 , i v = 0 4, i = 0 4 , i i = 1 2 , i i i = 1 4 , i v = 1 4, i = 1 4 , i i = 1 2 , i i i = 1 4 , i v = 0

MARKS App · Accepted Answer

Mother is a carrier (because her father is colour blind) and father is normal. Hence, their genotype is X c X and XY, respectively. Thus, the probability that their first child will be a normal son is 1/4, a carrier daughter is 1/4, colour-blind son is 1/4 and a colour-blind daughter is 0 (both husband and wife have normal vision, though 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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