Question

Explain the following.

Why colour blindness is more common in men than in women.

Answer 1

1. Colour blindness is more common in men than in women because it is a sex-linked recessive trait carried on the X chromosome. 
2. A male has only one X chromosome (XY), so if he inherits the defective gene on his X chromosome, he becomes colour blind.
3. A female has two X chromosomes (XX), so she becomes colour blind only if both X chromosomes carry the defective gene.

Therefore, colour blindness is more common in men than in women.