Instructions: Complete the following problems on lineless paper. Make sure you
show your work. Do not simply write down your answers. If you only write your answers you will not
receive full credit. Please number and letter your responses clearly. Also, clearly indicate the letter
symbols that you are using for each trait. Please highlight your final answer. Write legibly because if I
cannot read your work I cannot grade it.
1. In humans, PKU is an inherited metabolic disease, which if untreated, leads to death at about the age of
six. IT is inherited as a recessive trait. What is the probability that two heterozygous parents will have a
A) a PKU child? B) a heterozygous child? C) a homozygous non-PKU child?