16.5 Gene therapy

There are 4000 genetic diseases, and around 2% of the population are affected by one of them.

Cystic Fibrosis

This condition is caused by the deletion of three adenine bases from a gene called the CFTR gene. This means there is a missing amino acid which prevents the protein from functioning properly. The function of this protein is that it acts as a carrier to allow chloride ions to flow out of the epithelial membranes, then causing water to flow in through osmosis, making the epithelial membrane moist.

People with cystic fibrosis will have dry epithelial membranes, this means the mucus they produce is viscous and sticky, causing these problems:

• Greater risk of infection as mucus in the lungs is hard to remove and collects dust and disease.
  
  
• Less efficient gas exchange for the same reason.
  
  
• Sperm ducts may fill with mucus causing possible infertility.
  
  
• Fibrous cysts are formed in the duodenum due to pancreatic ducts being filled with mucus, preventing the release of pancreatic enzymes.

Treatment

Gene replacement: The faulty gene is replaced.

Gene supplementation: The correct gene is placed into the body and this will work ahead of the recessive gene as it is dominant.

Germ line therapy: The gene is replaced in the fertilised egg, is currently banned due to ethical reasons.

Somatic-cell therapy: This is where the gene is replaced in effected areas such as the lungs. In the lungs the treatment must take place every few days due to lung cells dying and being replaced. They are now trying…