Discovery may help locate genetic diseases

Researchers at the Whitehead Institute for Genome Research in Cambridge, Massachusetts have found that the majority of people of Northern European ancestry are likely to be descendants of a tiny prehistoric population. They used a technique made possible by the Human Genome Project (HGP) to show that Northern Europeans went through a 'population bottleneck' between 27,000 and 53,000 years ago, and may be the descendants of as few as 50 individuals.

The finding may have important implications for research into genetic diseases. The technique used, called 'linkage disequilibrium' analysed segments of DNA that contain the same 'bases', or links. The HGP showed that only one in every 100 of these varied from person to person. Variations that make people different or prone to certain diseases tend to be found in groups, therefore they may be easier to identify than previously thought.

By comparing the variations that different people have, researchers hope to be able to identify the ones that cause a propensity for disease. The larger the blocks of variations, the easier it will be to detect disease genes. This will form the basis of a two-tier study which first approximates the location of disease genes. Then by comparing the smaller blocks of other populations studied, such as a group from Nigeria, researchers will be able to target a specific location. The blocks are larger in the Northern European population because of the 'bottleneck' that occurred. In larger populations the blocks of unchanged DNA are smaller because they get changed with every new generation. Comparing lengths of DNA thus provides an indication to the history of a population.