Why are individuals who are heterozygous for the cystic fibrosis allele inaffected by the disease?

Individuals who are heterozygous for the cystic fibrosis allele carry one normal copy of the CFTR gene and one mutated copy. Cystic fibrosis is an autosomal recessive disorder, meaning that two copies of the mutated gene are required for the disease to manifest. The presence of one normal gene allows for sufficient production of the CFTR protein, which helps regulate salt and water transport in cells, preventing the development of the disease in heterozygous individuals.