While everyone's genome is 99.9 percent identical, small differences contribute to an individual's risk of complex diseases, such as Alzheimer's, diabetes, or depression. "We need databases of literally millions of human genomes and concomitant clinical information to decipher the influences of nature and nurture," says Craig Venter, a scientific advisor for the prize.

Databases of human genomes could also speed up drug development, by showing scientists what molecules to target and allowing them to test new drugs in groups genetically selected to be the most likely to respond.

Experts hope the prize will also bring public awareness to the legal and ethical issues that might arise when genome sequences become a common part of an individual's medical records. "It will open all sorts of new debates about privacy and ethics, debates Congress ought to have," says Billy Tauzin, a former congressman and lobbyist for the pharmaceutical industry. A bill prohibiting discrimination based on genetic information was passed in the U.S. Senate two years ago, but has not yet come up for vote in the House.

The X Prize project will have a number of celebrity participants--an addition perhaps designed to make up for the fact that rapid genome sequencing doesn't have the inherent excitement of a rocket launch. The first group to meet the goal of 100 genomes in 10 days will sequence an additional 100 genomes, including the DNA of celebrities and members of the public chosen by patient-advocacy groups. One of the first volunteers was Stephen Hawking, who suffers from Amyotrophic lateral sclerosis, a debilitating neurological disease thought to have genetic roots.