Cystic fibrosis and genetic screeningEdexcel International A Level Biology: Mind map

Exam questions on Cystic fibrosis and genetic screening

1. Cystic fibrosis (CF) is caused by mutations in the CFTR gene on chromosome 7. The most common mutation, called ΔF508, is the deletion of three bases from the gene. The CFTR protein is found in the cell surface membranes of epithelial cells lining the airways, pancreatic ducts and reproductive tract.
   Explain how the faulty CFTR protein causes the mucus made by epithelial cells to become thick and sticky.2 marks
2. A hospital respiratory clinic monitors a group of young patients with cystic fibrosis. Many have a persistent cough, produce large amounts of sticky sputum and are admitted several times a year with bacterial chest infections. Lung function tests show that the volume of air they can breathe out in one second is lower than normal.
   Explain why these patients have difficulty obtaining enough oxygen for their blood.2 marks
3. A cystic fibrosis clinic treats patients of all ages. One patient, a 9-year-old girl, is underweight despite eating a high-energy diet and passes pale, bulky, fatty stools. A scan shows that her pancreatic duct is blocked with thick mucus. Another patient, a 29-year-old man with cystic fibrosis, produces sperm normally in his testes, but no sperm are found in his semen. His wife does not have cystic fibrosis.
   Use the information to explain why the girl is underweight and passes fatty stools.3 marks