Question 3
A colour-blind man marries a woman who is homozygous for normal colour vision. What are their daughters like?
The right answer is the one marked above.
All have normal vision and all are carriers. Each daughter receives her father’s only X, which carries the recessive allele, and her mother’s XC, which masks it.
None of his sons carries the allele at all, because each receives his Y. The condition reappears in the grandsons, through the daughters.