Genetic modification - Uses in medicine

In genetic modification (GM), a gene is transferred from one organism to another, where it continues to work. This can be useful in biotechnology because a gene that codes for a useful protein can be inserted into a bacterium or yeast cell - which then multiplies many times and produces a lot of the desired protein. This protein is sometimes a medicine, for example, insulin.

Making insulin

Type 1 diabetes is a disorder in which the body doesn't produce enough of the hormone insulin. This means the blood glucose levels cannot be controlled effectively. It can be treated by injecting insulin. The extra insulin allows the glucose to be taken up by the liver and other tissues, so cells get the glucose they need and blood glucose levels stay normal.

GM insulin

Natural insulin can be taken from the pancreases of pigs or cattle. However, this insulin causes adverse reactions in some people and its supply is limited.

Nowadays, most insulin is made using genetically modified bacteria that have had the human gene for insulin inserted into them.

This GM insulin has some advantages over insulin taken from pigs or cattle:

  • it can be made in very large amounts from bacteria grown in a fermenter
  • it is less likely to cause an adverse reaction
  • it overcomes ethical concerns from vegetarians and some religious groups

Gene therapy

Gene therapy involves inserting copies of a normal allele into the chromosomes of an individual who carries a faulty allele. It is not always successful, and research is continuing.

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 enzymes 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
A diagram showing how gene therapy works. Normal alleles are copied then introduced to an affected cell.

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

Ethical considerations

It is illegal to genetically modify sex cells, such as sperm, because any changes would be inherited by the individual's offspring. Gene therapy is still not always successful and if the process caused a mutation in the DNA of the sex cell then this would be present in all of the cells of the 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.

Some people might not agree with changing a person's DNA.