Question

Girl of normal vision whose father was colour blind marries a man of normal vision whose father was also colour blind. The sons of this marriage would be.

• A. All normal
• B. All colour blind
• C. $50\%$ colour blind
• D. $25\%$ colour blind

Answer 1

Answer: (C)

$50\%$ colour blind

The woman is not color-blind, but her father was. This means she is a carrier of the gene. She marries a man that is not color blind, and thus doesn’t carry the gene at all. If they have children:

If they have a son, the chance to be colourblind is 50%.

If they have a daughter, the chance to be a carrier is 50%.

So, the correct answer is '50% colour blind'.