Question

Colour blindness in which all colours appear grey is?
a. Monochromatism
b. Dichromatism
c. Protonopia
d. Deuteronpia

Answer 1

Hint: Colour blindness is a recessive sex-linked defect in which human beings are unable to distinguish certain colours like red and green. It is caused due to mutation of x-linked genes.

Complete answer:
> Monochromatism
It is the condition in which a person is unable to see any color and everything appears to him grey. The only color he is able to see are black, white and different shades of grey. It may happen either because the cones of the eye that perceive color are damaged in that person or he is unable to translate the information received from cones due to some kind of defect in his nerves.

> Dichromatism
It is another type of color blindness in which the person lacks one type of cone pigments and has only two functional cones. So he is able to distinguish only two of three fundamental colors.

> Protonopia
In this type of color blindness, the person lacks the red cones. It is also called red-green color blindness. Such a person is not able to perceive red and green color.

> Deuteronpia
It is the type of color blindness in which the person lacks cones containing opsins that perceive green color so as a result, he is unable to distinguish red color from green color.

Hence, the correct answer is option (A).

Note: Color blindness occurs in about 8% of males and 0.4% of females as males have only one X-chromosome while females have XX. So in females, the effect of X-linked recessive allele is suppressed by her matching dominant allele.