Doctors long have known that diabetes is hereditary. But recent human genome research provides an instructional manual on the causes and health impacts of the disease.

And it's only a matter of time before science figures out how 30 newly identified genes cause or contribute to diabetes, and the best way to treat the many health problems they create.

Dr. Francis S. Collins, director of the National Human Genome Institute at the National Institutes of Health in Bethesda, Md., said little was known previously about the genetics of diabetes types 1 and 2.

But genome research last year brought "an explosion" of information about both types, along with previously unknown subtypes.

Genes long suspected of being involved with diabetes proved their innocence. Instead, 14 other genes have been linked to type 1, with 16 genes associated with type 2, with no DNA crossover.

The human genome is the full collection of 20,000 human genes, which contain the biological information needed to create and sustain a person. A gene, consisting of DNA, determines a characteristic in a person, and when changes occur in the DNA, disease can result, as happens with diabetes.

"We now have an instruction book that shows what enabled the glitches in the genome" that can prompt diabetes, Dr. Collins said. "What was stunning with the comprehensive look across the genome was what genes turned out to be involved.

"It was a complete surprise," he said.

Dr. Collins is co-chairman of the conference "Therapeutic Insights From New Diabetes Gene Discoveries," which concludes today in Philadelphia, where leaders in the field are outlining a strategy to unravel the complex genetic puzzle of diabetes, with eventual hope of new treatments.

Within two to four years, he said, researchers will better understand what causes diabetes and its subtypes. In 15 years, new understanding of both types will help to identify people at risk and outline lifestyle changes and new medications to treat them before onset.

Diabetes causes high blood-sugar levels that result from a person's inability to produce or properly use insulin. About 21 million people in the United States have diabetes with an epidemic of type 2 now under way.

Type 1 is an autoimmune disease that destroys or damages insulin-producing beta cells in the pancreas. In type 2, people either cease producing enough insulin or grow insensitive to the insulin they do produce.

The recent genetic breakthroughs could bring cures for types 1 and 2: "I wouldn't rule it out at all," Dr. Collins said. "And it may come from a direction we can't currently predict."

Most of the genetic discoveries in diabetes occurred in the past year, with some research yet to be published.

"It's very fresh," he said. "We knew genetic factors had to be there because type 1 and type 2 run in families. But now we have our eyes on specific genes. It's a huge leap forward."

Dr. Collins said studies already show that one gene controls a protein that transports zinc to the pancreas for use in storing insulin in crystals. The zinc transportation system works improperly in type 2, which represents a new finding.

Another newly discovered gene prompts cell division with implications for diabetes, heart disease and cancer. Dr. Collins said researchers were startled to find a direct link to all three diseases.

"I think this is an enormously exciting time," Dr. Collins said, noting that Science magazine judged diabetes gene research to be the top discovery of 2007. "This is our best window into the molecular basis of a very puzzling and complicated disease -- the fundamental problem and what gets it going."