Question

If a colour blind female marries a man whose mother was also colour blind, what are the chances of her progeny having colour blindness?

• A. 25%
• B. 50%
• C. 75%
• D. 100%

Answer 1

Answer: (D)

100%

Answer 2

The correct answer is (d).
Colour blindness 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. The female is colour blind which means she is homozygous (XCXC) for the disorder. The man she is marrying is also colorblind (XCY). Males have only one X chromosome and females have two. The XC in male is coming from his mother’s side.
If a female (XCXC) marries a man (XCY), the chances of her progeny having color blindness is 100% . If they have girls, all of them will be getting diseased X chromosomes (one from mother and one from father). If they have boys, all of them will be getting the diseased X chromosome from their mother.