How+Does+the+Gene+Work?

= Genetics =

====The Cystic Fibrosis transmembrane regulator protein is located on chromosome 7. It is a large gene that codes for 1480 amino acids. As a functional protein, its job is to transport chloride ions across the membrane. When the chloride ions leave the cell it creates a hypotonic environment which causes water to leave the cell by osmosis, diluting the mucus on the outer surface of the cell. Without this protein, the mucus does not have the aid of water to dilute it, causing it to thicken and build up. This mucus lines the vessels that not only fill the vessels but can also be an optimal breeding ground for bacterial growth that can cause immune, digestive, and respiratory problems (Lee, Tim W. et al., 2005). ==== ====If an individual has even one copy of the normal CFTR gene, that individual will not express the illness but will be a carrier. A carrier indicates that the individual has one copy of the mutated gene, thus has the ability to pass on the mutation to their children and is found in one out of twenty people. ==== ====If these carriers (called heterozygotes) have a child, there is a twenty-five percent chance they will develop cystic fibrosis because two copies of the mutated gene must be present (see picture, grey). ====

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=Mechanism = ====The central dogma of biology states "DNA makes RNA makes protein". The function of the protein is directly related to its how it is built. This means that the types and sequences of amino acids used will determine how the protein works. When creating proteins, a mutation can cause an incorrect amino acid to be used or the creation process to be halted prematurely. There are more than sixteen hundred mutations that have been identified to lead to cystic fibrosis and can be broken down into six different classes (Hopkins, 2006). ====

**Class 1**
====The mutation causes a premature termination (nonsense mutation) of CFTR protein. These mutations produce few or no functioning CFTR chloride channels. ====

====The most common of these mutations is named the F508 deletion. It is named as such because a missense mutuation occurs in the genetic code that deletes the five hundred and eighth amino acid, phenylaline. This missense mutation folds the protein incorrectly which inhibits it from ever reaching the membrane of the cell, where it would normally function (Rowe, 2011). ==== ====Another significant mutation that accounts for ten percent of all cystic fibrosis cases is W1282X. This mutation prematurely stops protein synthesis where the amino acid tryptophan would usually reside. This mutation is the cause of forty percent of the mutations in individuals of Israeli descent (Rowe, 2011). ====

How can Cystic Fibrosis be identified and treated? >>

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