Cystic fibrosis (CF) is caused by a defective gene and its protein product.  The gene is called CFTR, and it is on chromosome 7. CFTR stands for cystic fibrosis transmembrane regulator.   Normally, this gene makes a protein that is responsible for controlling water and salt movement in and out of cells. This protein sits on the membrane to regulate control.  It lets ions, such as chloride, through the cellular membrane by acting as a channel. 






The gene becomes defective when a mutation occurs. The mutation happens when three out of the 6100 letters are missing. This mutation is called delta-F508, since three letters are missing, the correct amino acid cannot be placed at the 508 position. Phenylalanine should be placed at the 508 position, but it will not occur, resulting in the gene being defective.  This can result in an abnormal CFTR protein or not one at all.  If a CFTR protein is made, usually the cell will destroy it because it recognizes it as abnormal. 






An abnormal CFTR or missing CFTR results in saltier sweat because chloride ions are not regulated. The chloride ions cannot pass through because the CFTR protein will not open.  If there is no protein, chloride ions will not be controlled.  This occurs mostly in sweat glands, altering concentration of ions, which affects other systems in the body.











http://www.linkstudio.info/portfolio/illustration05.htm (picture)


http://www.ygyh.org/cf/cause.htm- this website gives a great animation to explain how CF occurs!


















Sources:
http://www.ygyh.org/cf/cause.htm


http://www.cff.org/AboutCF/


http://www.childlifesociety.org/what_causes_cf.php