Question

I need help pls...
If a man has red-green color blindness, a sex-linked dominant trait, what is a possible genotype of his father? I. XR Y II. Xr Y III. XR XR IV XR Xr A. Only III B. I and III C. I and II D. I, III, and IV

Answer 1

Answer:

C

Explanation:

The possible genotype of his father is $X^RY$ and $X^rY$.

For sex-linked traits, an affected man always inherit the affected allele from the mother. The other chromosome, which is the Y chromosome is always from the father and this confers maleness on individuals.

The father of a man affected for a sex-linked trait can be affected for the same trait or otherwise. It does not have any bearing on the male child since the father only donates the Y chromosome to the male child.

Hence, in this case, the father can either be affected for the same trait ($X^RY$) or be free from it ($X^rY$).

The correct option is C.