The reality is sobering. Ten to 15 years ago we thought that we would be using genetic tests to predict all sorts of diseases, said Prof Tim Spector, a genetic epidemiologist at Kings College London. It turns out to have been wishful thinking.

We used to think there might be five to 10 genes involved in a disease, but we now know there may be thousands that only contribute a tiny amount and interact with each other.

It was hoped that the 1.8 billion human genome project to decipher our DNA would herald a new age in medicine when it was completed 13 years ago. Instead, it revealed that our genetic make up is far more complicated than we had expected.

None the less, scientists have now developed tests for about 2,500 diseases, but almost all are for rare conditions and only a fifth are treatable. Examples include Huntingdons Disease and Cystic Fibrosis.

However, scientists who worked on the human genome project are now striving to unravel the web of genes that play a role in more widespread conditions including obesity, diabetes and autism.

They are analysing the genomes of more than 10,000 people from around the UK who suffer from a range of diseases.Their results are already identifying genes that have weak effects in serious and common conditions.

These may not be useful as a test in themselves, said Dr Jeff Barrett, group leader on the UK10K project at the Wellcome Trust Sanger Institute. But they will help us understand more about these diseases. This can give us clues about how to develop treatments and to develop new ways of screening.

Also on the horizon are new tests for, diabetes, early-onset Alzheimers disease and colon cancer, which may help doctors provide treatments to slow them or prevent them from occurring.

Tests for obesity genes can also present people with the option of changing their behaviour and diet to reduce their chances of becoming obese.

Simultaneously, the development of genetic tests is also resulting in a growing ethical and moral debate about how they should be used. By providing seemingly healthy individuals with a warning that they may suffer from an illness later in their life, doctors are also offering them the chance to prevent it.

More here:
Where is genetic testing taking us?

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