Question

Probability with Huntington's disease?
Huntington disease is a rare degenerative human disease determined by a dominant allele, HD. The disorder is usually manifested after the age of 45. A young man has learned that his father has developed the disease; his mother does not have the disease (and does not carry to HD disease allele).
What is the probability that the young man will later develop the disease?

I went for 50%?

If the young man has a child with a woman who does not carry the HD disease allele, what is the probability that their first child will be affected by Huntington disease as

Answer 1

Check this out: http://uk.answers.yahoo.com/question/index?qid=20111201132717AARTsnN

Same question and there is an answer:
"You're correct that the man has a 50% probability of carrying the Huntington's allele.

Now, if he does have it, the probability that his first child will also inherit the Huntington's allele is also 50%. But there is only a 50% chance that the man has it to give to his son. So:

.5 X .5 = 0.25 = 25%

There is a 25% chance that the man's first child will be affected by Huntington's disease."

Answer 2

yep, exactly.