Why are some persons colour-blind? What is the cause of this defect?

1.	Why are some persons colour-blind? What is the cause of this defect?
Answer» In the retina of some persons, cone-shaped cells responding to certain specific colours are absent. Hence, these persons are unable to distinguish between certain colours, i.e., they are colour-blind.

Answer»

In the retina of some persons, cone-shaped cells responding to certain specific colours are absent.

Hence, these persons are unable to distinguish between certain colours, i.e., they are colour-blind.

Discussion