Question

What would be the nature of children, if a colourblind woman marries a normal man?

• A. Colourblind daughter and normal sons
• B. Colourblind sons and carrier daughters
• C. Normal sons and carrier daughters
• D. Normal sons and normal daughters

Answer 1

Answer: (B)

Colourblind sons and carrier daughters

Colour blindness is a X-linked recessive disorder. One copy of the affected gene in males in each cell is sufficient to cause the disorder (X${}^c$Y). Females with two copies of the affected gene show the disorder (X${}^c$X${}^c$). Females heterozygous (X${}^c$X) for this trait be normal but serve as a carrier of the disease. According to the question, the female is colour blind (X${}^c$X${}^c$) and father is normal (XY). The affected mother for colourblindness will inherit the disease to 100% sons (X${}^c$Y) while the 100% daughters will have normal vision but will serve as carriers. Correct answer is option B.