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Cystic Fibrosis

The Genetic Basis Of Cf

CF is a homozygous recessive genetic disorder. In this type of disorder, two defective copies of the gene, one from each parent, must combine to produce the disease. If two people who each carry the defective copy of the gene have a child, chances are that one in four of their offspring will have CF.

In 1989, a team of researchers located the defective CF gene, which was found to be located on chromosome 7. Genes are segments of deoxyribonucleic acid (DNA) that code for certain proteins. If the sequence of DNA mutates in a gene, the protein for which it encodes also can change. In CF, a change or mutation in the DNA sequence of the gene can lead to the production of a defective version of an important protein. This protein is called the cystic fibrosis transmembrane conductance regulator, or CFTR. The protein works as an ion pump within the cell membrane and regulates the movement of sodium and chloride (electrolytes that makeup salt) into and out of cells. In people with CF, this pump does not work properly. As a result, water is retained within the cells. A dry, sticky mucus builds up in the tissues that are affected.

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