Map of 'genetic signposts' may help to provide cures for cancer and diabetes

Analysis of genetic differences between three racial groups has given scientists one of the greatest potential insights into the nature of some of mankind's more intractable illnesses, from heart disease to mental disorders.

Analysis of genetic differences between three racial groups has given scientists one of the greatest potential insights into the nature of some of mankind's more intractable illnesses, from heart disease to mental disorders.

Researchers have itemised the smallest possible variations in the DNA of 71 individuals from European, African and Chinese origins to unravel the role of genes in diseases common to all humanity.

It is the first detailed map of some of the vital "genetic signposts" in three groups of people from different ethnic backgrounds. The signposts will ultimately point scientists toward finding the causes and treatments for illnesses including diabetes and cancer.

Such maps will also help doctors to prescribe more effective drugs targeted at an individual's genetic make-up, as well as help to understand why some people are more prone to certain illnesses than others.

David Hinds, of Perlegen Sciences, a biotechnology company in Mountain View, California, who led the research team, said yesterday: "We've created the first detailed map of common genetic variation in humans."

But he warned that the pioneering research should not be used to justify racial classifications, because genetic differences they have detected between ethnic groups are relatively minor, with everyone on earth sharing more than 99.99 per cent of their DNA blueprint.

He said the analysis of genetic differences would not resolve the continuing dispute in science about whether races are a genuine biological phenomenon rather than a cultural artefact. "Our study was really designed to help us understand patterns of [genetic] variation that are common and cut across populations," Dr Hinds added.

"People cannot use our data to say, 'see, I told you there are races', or, 'see, I told you there aren't races'," Dr Hinds told the American Association for the Advancement of Science in Washington DC. "Nor can they say, 'see, the differences are more important than the similarities'. But these data will be useful for starting to address such questions on which kinds of medical treatments should be used, based on physiological differences that are caused by genetic variations."

The Perlegen scientists, who publish their findings today in the journal Science, concentrated on identifying the smallest possible mutations that distinguished each of the 71 individuals in the study. They mapped 1.58 million of these "single nucleotide polymorphisms" (SNPs) on each person's set of chromosomes.

Scientists believe the reason why some people respond well to certain drugs and others do not is largely due to differences in these SNPs, or "snips" as they call them. Equally, snips may account for why some people get heart disease or cancer early in life and others with a less healthy lifestyle live longer.

Most of the 1.58 million snips were common to all three ethnic groups. For instance, 94 per cent of the snips were found in both of their variants in the African Americans in the study, 81 per cent were in both variants in the European Americans and 74 per cent in the Chinese American group. The company, which is collaborating with publicly funded research institutes in America working on the same problem, found seven million of the most common snip mutations were within just 5 per cent of the entire human population. A further four million snip mutations are less common, turning up in between 1 and 5 per cent of the world's population.

David Atshuler, a geneticist at the Massachusetts General Hospital in Boston, said a genetic map of the snip mutations would help doctors to understand the nature of disease. "The biological insights should be of tremendous value," he said. "In addition to the potential utility for disease research, such data are a spectacular resource for population and evolutionary geneticists."