Final answer:
The statement is false; heterozygous carriers of the CFTR allele, who have one normal and one faulty allele, do not exhibit the symptoms of cystic fibrosis as they produce enough functioning protein.
Step-by-step explanation:
The statement that heterozygous carriers of the CFTR allele exhibit the symptoms of cystic fibrosis is false. Individuals with cystic fibrosis must inherit two faulty CFTR alleles, one from each parent, meaning they are homozygous for the recessive allele (ff). Heterozygous individuals (Ff), who inherit one normal allele and one faulty allele, typically do not show symptoms of cystic fibrosis because they produce enough functioning CFTR protein to maintain normal pulmonary function and mucus secretion. Carriers can pass the mutant allele to their children, but they remain asymptomatic.
For instance, Zoe, who has cystic fibrosis, must have inherited two faulty CFTR alleles, one from each of her parents. Both of her parents are carriers but do not have the disease themselves. Thus, a child of two carrier parents has a 25% chance of having cystic fibrosis, a 50% chance of being a carrier like their parents, and a 25% chance of inheriting two normal alleles.