DNA sequences start to unravel the secrets of race and genetics

The most exclusive status symbol around is owned not by a super-rich playboy, but by a couple of scientists. While it should soon be possible to sequence anybody's entire genetic code for as little as £1,000, the only people who have yet had the privilege of reading every letter of their DNA are Jim Watson and Craig Venter.

The pair may well be the best-known living geneticists - and certainly the most controversial. Watson, the co-discoverer of the double-helix, is famously outspoken and politically incorrect. Venter, whose private effort to map the human genome triggered the fiercest scientific row of the past decade, is now attempting to create artificial life.

One of the first comparisons of their DNA, published yesterday by Venter's research team, does not reveal whether the two men share genes that explain their almost limitless capacity for starting fights. But it has shed important light on one of the main ways in which genetics might improve public health: predicting how patients will respond to drugs.

How the human body metabolises medicines depends heavily on genes, particularly those in a group called the CYP family. Variants that people inherit explain why some need very high doses of the blood-thinner warfarin that would be life-threatening to others. Others can predict how people will do when given antidepressant or antipsychotic drugs.

It is also known that these genetic variants differ in frequency between different ethnic groups, and this can be a useful tool for doctors. Venter, however, has always doubted whether race is a meaningful concept in science and medicine. His team's comparison of his genome and Watson's, published in Clinical Pharmacology and Therapeutics, illustrates why.

Both men are white, and might be expected by the rules of ethnic medicine to have the same CYP genes. But they don't. Venter has variants that suggest his body is good at processing antidepressants and the painkiller codeine. Watson's genome suggests he would respond less well, and might need higher doses for effective treatment.

No doctor would have guessed this from the colour of their skin. While race can be a helpful proxy for genes, it is an unreliable one. Ethnic medicine thus risks denying patients a helpful drug, because their genes do not match the group norm. It will also soon be obsolete, because Venter and Watson are not going to remain the only people with personal genetic read-outs for long. The cost of sequencing a genome is already down to about £30,000. As it falls further, it will become possible to prescribe to all patients according to their genes instead of their race.

Venter's new study certainly highlights the medical value of doing this, but I'm sure that isn't the only reason why he began it. He will also have been delighted to tweak his rival's tail. Jim Watson, you may remember, has expressed rather unsavoury views on race: last year, he suggested that Africans are less intelligent than Westerners. Venter, who was one of his biggest critics, has now used Watson's own genome to show up the limits of racial stereotyping. There is mischief as well as mastery in this man's science.