What is the genetic cause of cystic fibrosis?

Cystic fibrosis is primarily caused by a deletion in the CFTR gene, which encodes for the cystic fibrosis transmembrane conductance regulator protein. This deletion typically involves the loss of three nucleotides, resulting in the absence of phenylalanine at position 508 of the protein, commonly referred to as ΔF508. This mutation leads to the misfolding of the CFTR protein, which results in its improper trafficking to the cell surface and diminished chloride ion transport across epithelial cell membranes. Consequently, this disruption causes the various clinical manifestations associated with cystic fibrosis, including thickened mucus production, chronic respiratory infections, and pancreatic insufficiency.

Other potential causes listed, such as point mutations in BRCA1, chromosomal translocations, and single nucleotide polymorphisms, do not pertain to cystic fibrosis. BRCA1 mutations are associated with breast and ovarian cancers, while chromosomal translocations are often implicated in cancers like leukemia. Single nucleotide polymorphisms are variations in a single nucleotide that may or may not affect gene function but do not specifically lead to cystic fibrosis. Therefore, the genetic basis of cystic fibrosis is uniquely tied to the deletion in the CFTR gene.