Principles of Inheritance and Variation Question 144
144. A colour blind man marries a woman with normal sight who has no history of colour blindness in her family.
What is the probability of their grandson being colour blind?
[2015 RS]
(a) 1
(b) Nil
(c) 0.25
(d) 0.5
Show Answer
Answer : c
Hints & Solution
(c) 
The daughters of this couple will have normal eye sight but would be carrier. If one of the carrier daughter marries with normal eyed man,
Only 25% grandson will show colourblindness
