6.12 The Human Genome Project

The project

Scientists from many countries worked together for over ten years to sequence all 3 billion base pairs of the human genome. They found about 20 000 genes, far fewer than expected.

Uses in medicine

• Finding alleles linked to disease: scientists can compare the genomes of people with and without a disease to find the variants that raise the risk, for example of some breast cancers, heart disease or type 2 diabetes.
• Genetic testing: people can be tested to see if they carry an allele linked to a disease. They can then change their lifestyle, or have more frequent check-ups to catch the disease early.
• Personalised medicine: some drugs work well in people with one variant but not another. Knowing a patient's genotype helps doctors choose the right drug and dose, with fewer side effects.
• New treatments: understanding which gene causes a disorder is the first step to new drugs or gene therapy.

Problems and concerns

• A test shows increased risk, not certainty, so it can cause worry about something that never happens, or false reassurance.
• People worry that insurance companies or employers could use genetic information unfairly.
• Testing and personalised drugs can be expensive.
• Some people may not want to know their risk of a disease that cannot be treated.