The son of a man who does not have Huntington's develops Huntington's after age

Huntington's disease has autosomal dominant inheritance, meaning that an affected individual typically inherits one copy of the gene with an expanded trinucleotide repeat (the mutant allele) from an affected parent.Since penetrance of the mutation is very high, those who have a mutated copy of the gene will have the disease. In this type of inheritance pattern, each offspring of an affected individual has a 50% risk of inheriting the mutant allele and therefore being affected with the disorder (see figure). This probability is sex-independent

A = Huntington's disease (son)

a = Normal (man)

Father must must recessive and have the genotype 'aa'

Mother must either have the genotype 'Aa' or 'AA' for the son to have the disease.

A cross between aa (Father) x AA (Mother) produces Aa (heterozygous carrier, son)

A cross between aa (Father) x Aa (Mother) produces Aa (heterozygous carrier, son)and aa.

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