Practicing Success

Target Exam

CUET

Subject

Biology

Chapter

Principles of Inheritance and Variation

Question:

Colour blindness is a:

Options:

Sex-linked recessive disorder

Sex linked dominant disorder

Autosomal recessive disorder

Autosomal dominant disorder

Correct Answer:

Sex-linked recessive disorder

Explanation:

The correct answer is Option (1)- Sex-linked recessive disorder

Color Blindness: It is a sex-linked recessive disorder due to defect in either red or green cone of eye resulting in failure to discriminate between red and green colour. 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. This is because the genes that lead to red-green colour blindness are on the X chromosome. Males have only one X chromosome and females have two. The son of a woman who carries the gene has a 50 per cent chance of being colour blind. The mother is not herself colour blind because the gene is recessive. That means that its effect is suppressed by her matching dominant normal gene. A daughter will not normally be colour blind, unless her mother is a carrier and her father is colour blind.