General biology question ?

[glxvr6turbo]

A man in his early twenties who is normal learns that his father has developed Huntington's Disease, a rare, fatal disease caused by a dominant allele, which usually manifests itself in middle age (since the disease is rare, it is safe to assume that he is heterozygous). What is the probability that the younger man wil also develop the symptons later in life? (His mother does not carry a dominant allele.)

[mith]

You should start by writing out the genotypes

[kcnq1ot1]

A man in his early twenties who is normal learns that his father has developed Huntington's Disease, a rare, fatal disease caused by a dominant allele, which usually manifests itself in middle age (since the disease is rare, it is safe to assume that he is heterozygous). What is the probability that the younger man wil also develop the symptons later in life? (His mother does not carry a dominant allele.)

probability is *

Mod Edit: no point of giving answers...