Which type of inheritance does Cystic Fibrosis (CF) fall into?

• A. Autosomal Recessive
• B. Autosomal Dominant
• C. X-Linked Recessive
• D. Polygenic Inheritance

Answer: (A)

Cystic Fibrosis (CF) is classified as an autosomal recessive condition because it arises when an individual inherits two copies of a mutated gene, one from each parent. In the case of CF, the gene affected is the CFTR gene, located on chromosome 7.

When an individual has one normal allele and one mutated allele for the CFTR gene (a carrier), they typically do not show symptoms of the disease. However, when two carriers have a child, there is a 25% chance that the child will inherit both mutated alleles, resulting in Cystic Fibrosis.

This pattern of inheritance highlights the requirement for both alleles to be defective in order for the phenotype to manifest, which is the hallmark of autosomal recessive inheritance. Understanding this genetic basis is crucial for genetic counseling and for making informed decisions regarding family planning for individuals who are carriers.