Question

If a colour-blind woman marries a person whose mother is colour-blind, then what is the probability of colour blindness in their offspring?

• A. 50%
• B. 100%
• C. 25%
• D. 75%

Hint:

For X-linked recessive disorders, a homozygous recessive mother and affected male produce 100% affected children.

Answer 1

The Correct Option is B

The probability of color blindness in their offspring can be determined using a genetic understanding of X-linked traits, such as color blindness. Since color blindness is a recessive trait found on the X chromosome, we will analyze the genetic makeup of the parents:

• A color-blind woman has two X chromosomes, both carrying the gene for color blindness. Genotypically represented as X^cX^c.
• The man, whose mother is color blind, might be a carrier of the gene. Since men have one X chromosome, he can either be X^CY or X^cY. However, he can't be color-blind without having received the X^c from his mother. Thus, he is X^cY.

Parental Genotypes	Woman: XcXc	Man: XcY
Offspring Possibilities	XcXc (Color Blind)	XcY (Color Blind)

All male and female children will inherit at least one X^c chromosome from the mother. Thus, all offspring will be color blind. Hence, the probability is 100%.