Most people in synthetic biology are engineers who have invaded genetics. They have brought with them a vocabulary derived from circuit design and software development that they seek to impose on the softer substance of biology. They talk of modules — meaning networks of genes assembled to perform some standard function — and of “booting up” a cell with new DNA-based instructions, much the way someone gets a computer going.

The first practical applications of synthetic biology may not be so far off. “The real killer app for this field has become bioenergy,” Dr. Collins says. Under the stimulus of high gas prices, synthetic biologists are re-engineering microbes to generate the components of natural gas and petroleum. Whether this can be done economically remains to be seen. But one company, LS9 of San Carlos, Calif., says it is close to that goal. Its re-engineered microbe “produces hydrocarbons that look, smell and function” very similarly to those in petroleum, said Stephen del Cardayre, the company’s vice president for research.

Synthetic biologists are well aware that, like any new technology, theirs can be used for good or ill, and they have encouraged open discussion of possible risks at their annual meetings.

One possible danger is bioterrorism. According to a report in Science, Blue Heron Biotechnology, a DNA synthesis company, has already received requests, which it rejected, for DNA sequences encoding a plant toxin and part of the smallpox virus. Synthetic biologists hope that self-regulation will head off government supervision that could be expected to come in a field that has such potential for mischief.

Evolution continually refines its creations by means of the naturally occurring mutations in DNA that are the raw material of natural selection. This propensity to innovate may not be so welcome to synthetic biologists, who seek stable systems. But they hope to spot mutations with error-detection algorithms and then go back to the original cells. “You can think of it as a re-boot,” said Ron Weiss, a synthetic biologist at Princeton.

Even if the mutation problem can be squelched, it remains to be seen how far synthetic biologists can wrest evolution’s strange system to entirely different purposes and whether the human organism is one they will propose to debug and upgrade.