Final answer:
A person with mild Cystic Fibrosis symptoms would have two mutated CFTR alleles, as CF is an autosomal recessive disorder requiring two copies of the mutated gene to express the disease.
Step-by-step explanation:
A person affected with mild Cystic Fibrosis symptoms could have two mutated CFTR alleles. Cystic Fibrosis (CF) is an autosomal recessive disorder, which means that both copies of the gene must be mutated for a person to express the disease. However, the severity of symptoms can vary, and some individuals may display milder symptoms than others.
Each parent contributes one allele to their offspring. In the case of CF, if an individual has one normal CFTR allele and one mutated allele, they are considered a carrier. They can secrete normal mucus and typically do not present with symptoms, but they can pass the mutated gene to their children. If both parents are carriers, there is a 25% chance their child will be affected by CF, inheriting one faulty allele from each parent.
Zoe, a hypothetical individual affected by CF, must have inherited two faulty alleles, one from each parent, both of whom must be carriers of the CFTR mutation. The chance of a carrier couple having an unaffected child is 75%, which can either be a non-carrier (25%) or a carrier without symptoms (50%).