Cystic Fibrosis, which is also known as mucoviscidosis, is the most common life-shortening disease passed genetically through the white population and occurs once in every 2,500 births. It is carried by a recessive trait by about three percent of the white population. Children of parents that both have the recessive trait have a twenty-five percent chance of getting Cystic Fibrosis, a fifty percent chance of receiving one of the recessive traits, and a twenty-five percent chance of being unaffected. This disease causes certain glands to give off large amounts of thick mucus, which can build up and block the ducts of the glands and passageways from the ducts to different organs. The organs that are vulnerable to damage from the build up of the mucus are the lungs, liver and pancreas. .
The gene that carries Cystic Fibrosis is the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and it is located on Chromosome 7. It was discovered in 1989 by Canadian researchers and the CFTR gene was identified by positional cloning and DNA linkage analysis.
Cystic Fibrosis is caused by a deletion in the CFTR gene of Chromosome 7. The normal nucleotide sequence in the CFTR gene is ATC, ATC, TTT, GGT, and finally GTT, but in many patients with Cystic Fibrosis the last Cytosine in the 507th amino acid and the first two Thymine of the 508th amino acid are deleted. The final Thymine of what was Phenylalanine, the 508th amino acid, joins with the Adenine and Thymine of the 507th amino acid, Isoleucine, and stays as an Isoleucine for the 507th amino acid, because ATT is an alternative way to encode it from ATC, then goes to the 509th amino acid, Glycine. Since Phenylalanine is missing, sodium and chloride pumps in the tissues of the organs malfunction and produce the abnormally thick and sticky mucus. .
The CFTR gene normally regulates the production of the CFTR protein. The protein controls the flow of chloride ions into and out of certain cell membranes of cells, like a channel, that line the passageways of the lungs, liver, pancreas, intestines, reproductive tract and skin.