Huntington’s Disease is an autosomal dominant genetic disorder, which means that in order to inherit the disease, only one copy of the defective gene is needed. A person receives 1 copy of genes from each parent, so besides sex chromosomes, each person has 2 copies of each gene. A parent with the defective huntingtin gene has a 50% chance of passing on the defective copy rather than a healthy copy, which means that every child who has a parent with the defective gene has a 50% chance of getting the defective copy.