Question

Of both normal parents, the chances of a male child becoming colour blind are

• A. No
• B. Possible only when all the four grand parents had normal vision
• C. Possible only when father's mother was colour blind
• D. Possible only when mother's father was colour blind

Answer 1

The correct option is D Possible only when mother's father was colour blind

Colour blindness is a X-linked recessive disease and the chance of a male child becoming colour blind of a normal parents is only when mother's father was colour blind. This is criss-cross inheritance in which genes are transferred to a child from his maternal grandfather through his mother.

So, the correct answer is 'Possible only when mother's father was colour blind'.