Question

A woman with normal vision, but whose father was colour blind, marries a colour blind man. Suppose that the fourth child of this couple was a boy. The boy will have which of the following conditions?

• A. Will be partially colour blind since he is heterozygous for the colour blind mutant allele
• B. Must have normal colour vision
• C. Must be colour blind
• D. May be colour blind or may be of normal vision

Answer 1

Answer: (D)

May be colour blind or may be of normal vision

If the father of the normal visioned woman was colour blind, she might be a carrier, XC Xc. If the man is colourblind, he will have a genotype Xc Y.
The offsprings: XC XC (carrier daughter), XC Y (normal son), Xc Xc (colourblind daughter) and Xc Y (colourblind son). Hence, the son may be colour blind or may be of normal vision.