Venter cautioned that the creation of artificial human or animal life is a long way off because the synthetic bacteriophage - the virus that was created - is a much simpler life form. Bacteriophages are viruses that infect bacteria.

The project was funded in part by the Department of Energy, which hopes to create microbes that would capture carbon dioxide in the atmosphere, produce hydrogen or clean the environment.

But the questions ethicists have raised about such work are numerous: Should we be playing God? Does the potential for good that new life forms may have outweigh the harm they could do?

Arthur Caplan, who heads the University of Pennsylvania's Center for Bioethics, says yes. This technology "is impressive. It's powerful and it should be treated with humility and caution," Caplan says, "But we should do it."

A genome is made up of DNA "letters," or base pairs, that combine to "spell" an individual's chromosomes. The human genome project was completed in April.

This summer, researchers at Venter's Institute for Biological Energy Alternatives bought commercially available strands of DNA and, using a new technology, coaxed them together to form a duplicate of the genome of a bacteriophage called phi X.

"It's a very important technical advance," says Gerald Rubin, a molecular geneticist at the Howard Hughes Medical Institute. "You can envision the day when one could sit down at a computer, design a genome and then build it. We're still inventing the tools to make that happen, and this is an important one."

Venter notes the synthetic bacteriophage has 5,000 base pairs in its genome. The human genome has 3 billion, so similar work in human form probably won't happen in this decade, he says.

To date, the largest genome that was synthesized was the 7,500-base-pair polio virus. But that was only semi-functional and took three years to complete.

The researchers chose to put the new technology into the public domain for all scientists to use. It will appear in the next few weeks on the Web site of the Proceedings of the National Academy of Sciences.

The technology raises safety issues, says David Magnus of Stanford's Center for Biomedical Ethics. Even putting it in the public domain is "a double-edged sword," he says. That presumes that allowing everyone access will keep the good guys ahead of the bad guys. "It's a gamble. .. It's a bet that everyone has a stake in," he says.