San Jose, Calif. ? Wanted: Your genes.

Hoping to link illnesses to genetics and lifestyle, the federal government is exploring the possibility of recruiting a half-million Americans to contribute their DNA and health information to an ambitious national “biobank.”

Some scientists consider the project a long shot, largely because billions of dollars are needed to fund it at a time when Congress is busy spending money on other things. And before any such study is launched, they say, Americans need protection from genetic discrimination.

Despite those challenges, the National Institutes of Health is cautiously testing the waters this spring, holding “town hall” meetings, focus groups, interviewing community leaders and conducting a national survey of 4,000 Americans.

Scientists have long collected DNA from individual families with histories of deadly disease to find patterns in who lives and who dies. And countries such as Great Britain and Estonia are beginning to compile health information and collect DNA from patients.

But a biobank of America’s vast and diverse population would offer a far richer treasure trove of data. The size and variety of donations could help reveal now-hidden links between genes, lifestyles and the environment.

The push comes from National Human Genome Research Institute director Francis S. Collins, who led the government’s project to sequence the human genome. He says that it’s time to learn the medical significance of all the differences in our genetic blueprint – and only a huge and varied sampling can do it.

Since the historic sequencing of the human genome in 2000, scientists have been seeking the next step, said Stanford University bioethicist Hank Greely. “We’ve hit a bit of a brick wall,” he said.