Question

question 4 of 16
a grandfather has an x - linked disease. his wife does not have the disease and she is not a carrier for it. what is the probability that their daughter’s sons will have the disease?
○ 0%
○ 50%
○ 75%
○ 100%
○ 25%

Explanation:

Step1: Determine grandfather's X chromosome

Grandfather has X-linked disease, so his X is diseased ($X^d$), Y is normal ($Y$). Wife is non-carrier: $X^N X^N$.

Step2: Deduce daughter's genotype

Daughter inherits $X^d$ from father, $X^N$ from mother → $X^N X^d$ (carrier).

Step3: Calculate grandson's probability

Daughter passes either $X^N$ or $X^d$ to son (50% each). Son gets Y from father, so disease if he gets $X^d$. Probability = 50%.

Answer:

50%