Question

A young man knows that his grandfather had Huntington disease (genotype Hh). However, his father passed away at the age of 26 without ever being tested or showing signs of HD. Neither the young man's mother nor his grandmother had Huntington disease. What is the probability that this young man will develop HD when he is older?

Answer 1

Answer:25%

Explanation:

Given

Grandfather had Huntington disease

So Probability that the father had inherited the disease is $\frac{1}{2}$

So the Probability that the young man will get the disease is equal to half of Probability that his Father had inherited the disease

i.e. $P=\frac{1}{2}\times \frac{1}{2}=\frac{1}{4}$

=25%