Question

A woman with normal vision has a colour blind father. She marries a man with normal vision. The percentage chance of their progeny being colour blind is:

• A. 0.25
• B. 0.5
• C. 0.75
• D. 1

Hint:

Colour blindness is an X-linked recessive trait. A carrier female has a 50% chance of passing the gene to her offspring.

Answer 1

The Correct Option is A

Since the woman has a colour-blind father, she is a carrier (XNXc). Her husband, having normal vision, has the genotype XNY. Their offspring will have the following probabilities:
- Sons (XY) will inherit their father’s Y chromosome and will not be colour-blind.
- Daughters (XNXc) will inherit one X chromosome from the mother and will be carriers (not colour-blind).
Thus, there is a 25 percent chance that a daughter could inherit the colour-blind allele, making her a carrier.