1.4.17 Explain how the expression of a gene mutation in people with cystic fibrosis impairs the functioning of the gaseous exchange, digestive and reproductive systems.

- The genetic disorder cystic fibrosis is caused by mutation of the gene that codes for the CFTR protein that allows chloride ions to pass through cell membranes,: water enters the cell because chloride ions cannot leave to create the correct concentration gradient for water to move out by osmosis and dilute mucus, so mucus becomes sticky and viscous. 

- In the gas exchange system (breathing problems & lung infections), mucus accumulates in the lungs, bacteria get trapped in mucus, increasing the possibility of infection. Mucus can also block bronchioles, which reduces the number of alveoli in contact w fresh air so reduced surface area for gas exchange.

- In the digestive system mucus blocks the pancreatic duct so digestive enzymes can’t reach the duodenum (small intestine) so food is not properly digested, leading to tiredness and difficulty gaining weight. Enzymes trapped within the pancreas causes fibrosed cysts and damage to insulin-producing cells, leading to diabetes.

- In the reproductive system ( ) in women the mucus can block the cervix preventing the entry of sperm, leading to a reduction in likelihood of pregnancy. In men the sperm duct is either missing or blocked with mucus, so sperm cannot leave the testes, leading to less sperm ejaculation than normal.