<P> ΔF508 (Delta - F508, full name CFTRΔF508 or F508del - CFTR; rs113993960) is a specific mutation within the gene for a protein called the cystic fibrosis transmembrane conductance regulator (CFTR). The mutation is a deletion of three nucleotides spanning positions 507 and 508 of the CFTR gene on chromosome 7, which ultimately results in the loss of a single codon for the amino acid phenylalanine (F). A person with the CFTRΔF508 mutation will produce an abnormal CFTR protein that lacks this phenylalanine residue and which cannot fold properly . This protein does not escape the endoplasmic reticulum for further processing . Having two copies of this mutation (one inherited from each parent) is by far the most common cause of cystic fibrosis (CF), responsible for nearly two - thirds of cases worldwide . </P> <P> The CFTR gene is located on the long arm of chromosome 7, at position q31. 2, and ultimately codes for a sequence of 1,480 amino acids . Normally, the three DNA base pairs A-T-C (paired with T-A-G on the opposite strand) at the gene's 507th position form the template for the mRNA codon A-U-C for isoleucine, while the three DNA base pairs T-T-T (paired with A-A-A) at the adjacent 508th position form the template for the codon U-U-U for phenylalanine . The ΔF508 mutation is a deletion of the C-G pair from position 507 along with the first two T-A pairs from position 508, leaving the DNA sequence A-T-T (paired with T-A-A) at position 507, which is transcribed into the mRNA codon A-U-U . Since A-U-U also codes for isoleucine, position 507's amino acid does not change, and the mutation's net effect is equivalent to a deletion ("Δ") of the sequence resulting in the codon for phenylalanine at position 508 . </P>

Dna changes that produce the abnormal cystic fibrosis protein