Colour blindness and haemophilia in human beings are due to:

Correct answer: (d) Recessive genes present on the X chromosome

Explanation

Colour blindness and haemophilia are both caused by recessive genes on the X chromosome (X-linked recessive disorders).

A male (XY) with one affected X chromosome has the disorder, because he has no second X to carry a normal copy. A female (XX) has it only if both her X chromosomes carry the gene; with one, she is a carrier. That is why both are far more common in men.