The human genome project and medicine

The genetic information in an organism is called its genome. The Human Genome Project, or HGP for short, was started at the end of the last century. It was very ambitious and had several aims, including:

  • to work out the order or sequence of all the three billion base pairs in the human genome
  • to identify all the genes
  • to develop faster methods for sequencing DNA

The sequencing project was finished in 2001, and work continues to identify all the genes in the human genome. The HGP used the DNA of several people to get a sort of average sequence, but each person has a unique sequence (unless they have an identical twin).

There is still a lot to learn about how we can use our knowledge of the human genome to help advance medical treatments. It is hoped that information from the Human Genome Project will allow scientists to develop new ways of treating or diagnosing illnesses, especially genetic disorders and cancer.

Genetic disorders

A person with cystic fibrosis has inherited two faulty alleles for a certain gene on one of their chromosomes, chromosome 7. It is hoped that it may one day be possible to repair the faulty alleles using gene therapy, perhaps by putting the normal allele into the cells of the lungs. This would greatly improve the lives of people with cystic fibrosis, who often need lung transplants as their illness progresses. By understanding the human genome in more detail, gene therapy for cystic fibrosis has become more likely.

Breast cancer

Members of some families are particularly at risk of developing certain types of breast cancer, because they carry faulty alleles. Following the HGP, these alleles have been identified. It is now possible to test people to see if they have these alleles in their DNA. This will predict the likelihood of them developing the disease. This process allows the person to make decisions, if they wish, about whether to have surgery to remove breast tissue before any cancer develops in their breasts. It also allows doctors to predict the chance of any offspring having the disease if both parents are tested for the alleles.

Huntington's disorder

Huntington's disorder is caused by a dominant allele. The symptoms usually develop in middle age, and include tremors, clumsiness, mood changes, memory loss and the inability to concentrate. Patients of Huntington's disease have often had children by the time their symptoms develop. By understanding the human genome, it is possible for offspring of the patient to choose to be tested and see if they have inherited the dominant allele.

Some people do not want to know if they will develop the disease and want to go on living their lives as normal. Other people feel better if they can prepare themselves for what is going to happen to them later on in life.

Targeted therapies – Cancer

A huge breakthrough in medicine has been the ability to sequence the DNA in cancer cells. The sequence can be compared to the sequence found by the Human Genome Project. This allows scientists to work out which genes are mutated and this gives them ideas for developing medicines. For example, it was found that certain breast cancers have a mutation in a gene called HER-2. By finding this out, scientists were then able to produce a monoclonal antibody that was specifically targeted to cancer cells that had the mutation. The treatment is very successful and could not have been developed without our detailed knowledge of DNA sequencing and the human genome.

Future hopes

It is hoped that more and more medicines can be developed now that the sequence of the human genome is known. Being able to target diseases with specific medicines, and using gene therapy to treat diseases on a patient-by-patient basis, will revolutionise modern medicine. Patients can also respond to drugs differently. Sometimes one disease can be caused by a variety of different mutations or risk factors. Pharmacogenetics is the study of an individual's genome to predict how they will respond to a drug treatment. This type of medicine will also help to make sure that drugs are only used if the doctors know they are going to work. This means the patient is more likely to respond to the drugs and also reduces the use of ineffective drugs, saving limited NHS resources.

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