Why colour blindness is found more in males than in females ?

The correct answer is Option (1) -Males have only one X chromosome, so a single defective gene causes color blindness.

Colour blindness is a recessive sex-linked disease. This defect is due to mutation in certain genes present in the X chromosome. It occurs in about 8 per cent of males and only about 0.4 per cent of females.

Color blindness is typically caused by a mutation on the X chromosome. Since males have only one X chromosome (XY), a single recessive allele for color blindness on this X chromosome will result in color blindness.

Females, on the other hand, have two X chromosomes (XX). For a female to be color blind, she would need to have the recessive allele on both of her X chromosomes. If she has only one affected X chromosome, she is a carrier but not color blind because the normal allele on the other X chromosome can compensate. This is why color blindness is more prevalent in males.