1. Gene technology in medicine is used in two main ways.
   1. Genetic engineering of microorganisms inserts human genes into bacteria or yeast so that they make human proteins that can be used as medicines.
   2. Gene therapy inserts working alleles into a patient's own cells to treat a genetic disorder.
2. Both uses rely on cutting out a gene and carrying it into another cell using a vector.
3. Each use brings benefits, but each also raises practical difficulties and ethical questions that have to be weighed up.

Medicines made by GM bacteria

1. The human gene for a useful protein, such as insulin, is cut out of human DNA and inserted into a plasmid, which acts as the vector.
2. The plasmid is taken up by bacteria, which become genetically modified.
3. The GM bacteria are grown in large fermenters, where they divide rapidly and every cell uses the human gene to make the human protein.
4. The protein is then extracted from the fermenter and purified so that it can be used as a medicine.
5. Other medicines made in this way include human growth hormone, used to treat children who do not grow normally, and the clotting factors needed by people with haemophilia.
6. Making medicines in GM bacteria has several benefits.
   1. Large quantities of the protein can be made quickly and cheaply, because bacteria reproduce so rapidly.
   2. The protein is identical to the human version, so it is less likely to cause an allergic reaction than insulin extracted from pigs or cows.
   3. The supply does not depend on animals being slaughtered, which some people object to for ethical or religious reasons.
   4. The products are free of human viruses, unlike some clotting factors that were once extracted from donated human blood.
7. There are also drawbacks.
   1. Building fermenters and purifying the product is expensive, so some of these medicines are still costly.
   2. The GM bacteria must be contained carefully, because some people are concerned about the effects if they escaped into the environment.

Gene therapy

1. Many genetic disorders, such as cystic fibrosis, are caused by a faulty allele that stops a cell making a working protein.
2. In gene therapy, a working copy of the allele is inserted into the patient's cells so that the cells can make the missing protein.
3. The working allele is carried into the cells by a vector, usually a virus that has been modified so that it cannot cause disease.
   1. Tiny spheres of lipid called liposomes can also be used, and these can be breathed into the lungs.
4. In somatic gene therapy, only body cells are changed, such as the cells lining the airways of a person with cystic fibrosis.
   1. The change is not passed on to the patient's children.
   2. Body cells are replaced over time, so the treatment may have to be repeated.
5. In germline gene therapy, the allele would be inserted into gametes or an early embryo, so every cell of the person would carry it and it would be passed on to their descendants.
6. Germline gene therapy in humans is not allowed in the UK.
7. Somatic gene therapy has already been used to treat a rare inherited condition in which children are born with almost no working immune system, and some inherited forms of blindness.

Practical considerations

1. It is difficult to get the allele into enough of the right cells, because a vector cannot reach every cell in an organ.
2. The allele may work for only a short time, especially in cells that are regularly replaced, so the treatment has to be repeated.
3. The patient's immune system may recognise a viral vector as foreign and attack it, which can cause inflammation and make repeat treatments less effective.
4. The inserted allele may enter the DNA in the wrong place and disrupt another gene.
5. In a few early trials, this caused some patients to develop leukaemia.
6. Gene therapy works best for disorders caused by a single gene, while most common diseases are influenced by many genes and by the environment.
7. Gene therapies are extremely expensive to develop, and a single treatment can cost hundreds of thousands of pounds.

Ethical considerations

1. Many people support somatic gene therapy, because it treats a patient who has given consent and affects only that person.
2. Germline gene therapy raises greater concern, because it changes future generations who cannot give consent.
3. Some people fear the same technology could be used to choose characteristics that have nothing to do with health, such as height or eye colour, producing so-called designer babies.
4. There is debate about who should decide which conditions are serious enough to be treated.
5. The high cost raises questions of fairness, because treatments may be available only in wealthy countries or to people who can pay.
6. Some people have religious or moral objections to changing human genes at all.
7. Others argue that it would be wrong not to use a technology that could prevent serious suffering.