Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!
Print

Science

Testing and treating genetic diseases

Gene therapy

Gene therapy involves inserting copies of a normal alleleallele: One form of a gene. into the chromosomeschromosome: One of the rod shaped bodies found in the nucleus of cells that contain genetic information (DNA). of an individual who carries a faulty allele. It is not always successful, and research is continuing.

It is illegal to do this to sex cells, because any changes would be inherited by the individual’s offspring. Instead, gene therapy is used on body cells. It means the individual could pass on their faulty allele to their children, even if they get better themselves.

The basic process

Gene therapy involves these basic steps:

  1. Doing research to find the gene involved in the genetic disorder.
  2. Cutting out the normal allele. Special enzymesenzymes: Proteins which catalyse or speed up chemical reactions inside our bodies are used to do this.
  3. Making many copies of the allele.
  4. Putting copies of the normal allele into the cells of a person who has the genetic disorder.
the normal allele is cut out, many copies are made, normal allele is put into cells

The gene therapy process

Problems in the process

The main difficulty is usually the last step. Here are some of the problems:

  • the alleles may not go into every target cell
  • the alleles may join with the chromosomes in random places, so they do not work properly
  • treated cells may be replaced naturally by the patient’s own untreated cells

Different methods

Different methods are used to get the alleles into the patient’s cells, including:

  • using fat droplets in nose sprays
  • using cold viruses that are modified to carry the allele - the viruses go into the cells and infect them
  • the direct injection of DNA [DNA: The material inside the nucleus of cells, carrying genetic information. DNA stands for Deoxyribonucleic Acid. ]

Back to You and your genes index

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.