NEETZoologyPrinciples of Inheritance and Variation
Why is the mother of a color-blind son not herself color blind?
Options
- AShe has two X chromosomes with normal genes
- BThe gene is dominant in females
- CShe has a dominant normal gene that suppresses the effect
- DShe has a different type of gene that prevents color blindness
Correct answer
C. She has a dominant normal gene that suppresses the effect
Step-by-step solution
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