question: What is needed for a person to be affected by an autosomal dominant disorder?
distractor3: one isolated allele
distractor1: extra alleles
distractor2: one less chromosome
correct_answer: one mutated allele
support: Autosomal Dominant Only one mutated allele is needed for a person to be affected by an autosomal dominant disorder . Each affected person usually has one affected parent. There is a 50% chance that a child will inherit the mutated gene. Huntingtons disease, Achondroplasia, Neurofibromatosis 1, Marfan Syndrome, Hereditary nonpolyposis colorectal cancer.