A landmark UK consortium of 50 research groups has identified new genetic variations linked to seven common diseases, opening the way for new treatments and genetic tests.
Researchers scanned the whole genome
What did they find?
They discovered 17 genetic variants - either individual genes or gene regions - across seven common diseases.
So far the most useful findings have been in type 1 diabetes and Crohn's disease but there was also a major genetic variant found to increase the risk of heart disease and several genes which increase a person's risk of developing type 2 diabetes.
Importantly they also confirmed that this type of whole genome association study can provide useful results.
It also underlines the belief that there are very few conditions caused by single genes but that diseases are more likely to be associated with many genes which each has a small effect.
What does it mean for patients?
Despite huge amount of medical research, scientists understand very little about the causes of many diseases.
It is hoped that these kind of studies will offer insights into the biological mechanisms underlying the disease and indicate new targets for research into treatments.
For example in Crohn's disease, the team did not expect to find that autophagy - a process of removing unwanted bacteria from within cells - was an important factor.
They now plan to study this further to find out if it is associated with specific bacteria and there are treatments available which effect autophagy that researchers can investigate for use in Crohn's disease.
It is also possible that scientists could develop tests for genes known to increase the risk of a certain disease.
A person would then know their lifetime genetic risk of a disease but environmental factors would still be important in determining whether they actually developed the condition.
How was it done?
Previous studies into the genetics behind disease have focused on rare inherited diseases such as cystic fibrosis.
A technique called linkage analysis would be used to analyse about 300 genetic markers in a small group of people, normally family members, and compare those with the disease against those who did not have it.
THE DNA MOLECULE
The double-stranded DNA molecule is held together by four chemical components called bases
Adenine (A) bonds with thymine (T); cytosine(C) bonds with guanine (G)
Groupings of these "letters" form the "code of life"; there are about 3 billion base-pairs in the human genome wound into 24 distinct bundles, or chromosomes
Written in the DNA are about 20-25,000 genes which human cells use as starting templates to make proteins; these sophisticated molecules build and maintain our bodies
The WTCCC, however, used "gene chip" technology, analogous to a microchip, to scan hundreds of thousands of DNA markers at once
This way they could look at the whole genome, to find differences in a large group of unrelated individuals - in this case 17,000.
The markers they used are called single nucleotide polymorphisms (SNPs) - common differences in single DNA bases that occur throughout the genome.
The researchers scanned 500,000 of these, although there are around eight million common SNPS in European populations.
Who was behind the research?
The Wellcome Trust Case Control Consortium (or WTCCC), was set up in 2005 with £9m funding from The Wellcome Trust, and is a collaboration of 24 leading human geneticists.
The charity also co-funded the earlier.
Human Genome Project and the International HapMap Project - a multi-country effort to identify genetic similarities and differences in humans - and it was hoped the WTCCC would build on this research to work out the genes that predispose people to several common diseases.