Cystic fibrosis (CF) is a genetic disorder. Sufferers have inherited ‘faulty’ genetic information from their parents and this makes them produce extra mucus. Mucus is a slimy substance that traps microbes. Normally, ciliated epithelial cells sweep the mucus out of your lungs and you swallow it. However, CF sufferers produce so much mucus that this does not happen. The mucus builds up in their lungs and they find breathing difficult. The mucus also encourages bacteria to grow and CF sufferers often get lung infections.

To get rid of this mucus, CF sufferers have physiotherapy sessions. A physiotherapist slaps them on the back to make them cough up the mucus and help them breathe better.

Most CF sufferers have problems with other organs too. Cystic fibrosis affects the pancreas. The pancreas produces enzymes which digest food. The extra mucus blocks the small tube leading from the pancreas to the small intestine and so the enzymes cannot get to the small intestine. CF sufferers take tablets containing digestive enzymes.

Not many people with CF live past 30 years of age, although with modern treatments more and more sufferers are living longer and longer.

For a person to have cystic fibrosis they must have a CF gene from their mother and a CF gene from their father. People who have only one CF gene are called carriers. Carriers are perfectly healthy, but two parents who are both carriers may have children who have cystic fibrosis. Half of the man’s sperm cells will contain the CF gene and the other half will contain the normal gene. The same is true for the mother’s egg cells. Half of her egg cells will contain the CF gene. One person in 25 carries this ‘faulty’ gene.

1How do people get cystic fibrosis?

2What builds up in their lungs and makes breathing difficult?

3What grows on the mucus that can be harmful?

4What is done to make the cystic fibrosis sufferer feel better?

5Give an example of an organ that may not work properly in CF sufferers.

6a What is a ‘carrier’?

b What percentage of people are carriers?

c Why do only half of a carrier’s gametes contain the faulty CF gene?

7a Draw a diagram to show how two parents who are both carriers can produce a child
who has cystic fibrosis.

b Explain why only 25% of their children get cystic fibrosis.

8Find out what is being done to ‘cure’ cystic fibrosis.