Huntington's disease is a degenerative disease of the nervous system, which, for most, does not show up until after age 40. It is caused by a dominant gene. While John's father (60, XY) was diagnosed with the disease ten years ago, he has just begun to show symptoms of the disease.

What is the chance that John (38, XY) and his brother (42, XY) will have the disease?
A) If John's mother is homozygous recessive and his father is heterozygous, there is a 100% chance he and his brother will have the disease
B) If John's mother is homozygous dominant and his father is heterozygous, there is a 100% chance he and his brother will have the disease
C) If John's mother and father are heterozygous, there is a 100% chance he and his brother will have the disease
D) John's mother and father are homozygous dominant, there is a 100% chance he and his brother will have the disease