AIIMS 2017 Botany Sex-linked Inheritance MCQ Question
A man whose father was colourblind marries a woman, who had a colourblind mother and normal father. What percentage of male children of this couple will be colourblind?
25%
0%
50%
75%
Correct Answer
Detailed Explanation
The man is colorblind, which means he has the genotype XᶜY (where Xᶜ represents the colorblind allele), and the woman, having a colorblind mother, must be a carrier with the genotype XᶜX (since her father is normal). Their male children inherit the Y chromosome from their father and one X chromosome from their mother, leading to potential genotypes of either XᶜY (colorblind) or XY (normal). Since the mother can only pass on the X chromosome, the male children will inherit either Xᶜ (colorblind) or Y (normal), resulting in 0% of their male children being colorblind.
Options A (25%), C (50%), and D (75%) are incorrect because they misinterpret the inheritance pattern; the male offspring cannot inherit colorblindness from the father, as it is linked to the X chromosome, which they do not receive from him.
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