Most of the "genes" these companies will test you for are actually gene markers that confer some risk that a person will contract a disease. Most of them have been collected by comparing a population of people with the disease to those who don't have the disease. That means that the information not necessarily relevant for you.

A person may test positive for a gene associated with colon cancer, but may also have five other genes that protect from this malady that are not picked up by 23andMe or deCodeMe. People may also contract the disease even when they lack the gene.

And what of people who discover their fathers are not really their fathers? Or that their parents' DNA combined to give them a gene associated with heart attack? What of people who may have given the breast cancer gene to their daughters?

Many physicians, geneticists and bio-ethicists believe that presenting a person's raw genetic information online with no interaction with a trained doctor or genetic counselor will confuse and scare some people.

They also point out that few standards exist to measure the validity and usefulness of some 15,000 genetic markers—including about 2,000 associated with disease.

The failure to provide such guidance and information lies squarely with the health care and research establishment, who have done little to organize themselves to handle the inevitability of a 23andme and deCodeme showing up to bypass them and go directly to consumers.

Doctors are untrained and hospitals and clinics have done little to integrate or understand these tests. No system exists that gauges the accuracy of genes that run the gamut from useful to highly speculative.

The government has left the space largely unregulated. Congress, the Food and Drug Administration, and the Federal Trade Commission have investigated some direct-to-consumer genetic tests, and have discussed the possibility of regulating the tests and the accuracy of the results.

At the moment, the sites are careful to say that they are not offering medical diagnosis or advice, though many customers will not understand the distinction.

Congress urgently needs to pass the Genetic Anti-Discrimination Act, passed by the House of Representatives earlier this year. President Bush has said he would sign it, but the bill is being held up by a single senator, Republican Tom Coburn of Oklahoma, a doctor who has placed a "hold" on a bill overwhelmingly supported by his colleagues.

The appearance of these new companies is ushering in yet another wave of Brave New World science that has the power to alter how we view ourselves, and perhaps our lives. It's an exciting moment that should be tempered with caution to be sure that this new information is accurate and delivered properly, but one thing is certain—the age of personal genomics is here, arriving like most technologies in fits and starts, but ultimately unstoppable.

_{Part 2 of this series will be published later this week as David Ewing Duncan runs his own DNA through the new websites and test-drives this Brave New world of genetic testing.}