Cellular Biology 3. What is cystic fibrosis? How does the most common allele of

Question

Cellular Biology

3. What is cystic fibrosis? How does the most common allele of the CFTR gene result in the symptoms associated with cystic fibrosis? What is allele that encodes the CFTR protein that is sensitive to treatment by the drug ivacaftor.

4. Dysfunction of the multidrug resistance transporter 1 (MDR1) has been implicated in both drug resistance and drug sensitivity, depending on the clinical situation. Explain what this transport protein is, how it normally functions, and how it can hamper the treatment of cancer or result in toxicity if not functioning normally.

Explanation / Answer

3. Cystic fibrosis (CF) is a genetic disorder, which occurs as a result of mutation in CFTR gene. The gene CFTR encodes for a protein, which moves chloride ions out of epithelial cells. This results in the concomitant efflux of water molecules along with chloride ions by osmosis. This process forms a thin film of water over the surface of the epithelial cells, which lets the mucus to slide away very easily.

The common mutation in CF is a deletion of one codon (three base pairs) of the CFTR protein; this deletion is called “F508.” Because of this mutation, the transport of chloride ions and water molecules across the cell membrane is disrupted. So, the epithelial cells are not kept wet as well as before. As a result, the mucus adheres to the walls of the body tubes instead of its normal slipping over body’s tubes. This result in the clogging of passage ways, so, the CF patients usually suffer from gastrointestinal and respiratory disorders. CFTR I allele encodes one protein that is ssensitive to treatment by the drug ivacaftor.

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