You are a geneticist who advises couples about the possible genetic disorders they could pass to their children. A married couple schedules an appointment with you, and they inform you that they are both heterozygous for Huntington's disease, an autosomal dominant trait. They are aware that this disease is incurable and lethal, and they don't want to pass it on to the 3 children they hope to have in the future. They ask you the probability all three will escape inheriting Huntington's. What do you tell them?