The students at Banneker High School in Washington sat riveted as Sir John E. Sulston, a Nobel Prize-winning geneticist and the British face of the Human Genome Project, pulled out a spool of thread, held one end of the strand and rolled the rest across his desk.

"The DNA thread is common to all of us," he said. "It is the code of life, a continuous thread of copying DNA that goes back 4 billion years to the first life-forms on the planet."

He later held up a compact disc. "This CD now carries the instructions to make a human being," he said.

About 30 advanced placement biology, chemistry and International Baccalaureate students had gathered in the Banneker library Friday to hear Sulston describe the heavy responsibility awaiting future scientists as a result of the decoding he helped bring about.

His sense of urgency was fueled in part by a battle royal fought three years ago to prevent Celera, a Rockville-based biotech firm, from privatizing genome data for profit.

"It was so awfully unbelievable," Sulston said. "This corporation wanted to put a fence around their private database, and only people who could pay, meaning only the very wealthy, would be allowed to come in and read the data."

Sulston prevailed, and the genome data are now part of the public domain. But other challenges remain.

At a time when science seems so heavily invested in bioterror and nuclear destruction, will America's young scientists maintain the wherewithal to fight for life-affirming discoveries?

"I believe that one of the big deals, perhaps the greatest deal in the world today, is the extreme imbalance of wealth, which means extreme imbalance in heath care," Sulston said. "We don't have corporations or venture capitalists putting up money to work on cures for, say, malaria, because that only affects the poor. Venture capital goes into things like antidepressants, which are sold in rich markets."

He called on the World Trade Organization and similar groups to "rebalance" international trade, adding, "this is a call certainly to America and all of Europe, the rich countries, to stop being quite so greedy and seriously start to even up the world, particularly in health care."

Sulston had visited Banneker with science writer Georgina Ferry, co-author of their book, "The Common Thread: A Story of Science, Politics, Ethics and Human Genome." The book was published by the National Academy of Sciences in Washington, which has a partnership with Banneker High.

"These students are the leaders of the future, and we want to strengthen our network," said Warren Muir, executive director of the NAS division on earth and life studies. As principal Patricia L. Tucker put it, "This partnership is one way we ensure that our students get a world-class education."

But to whom much is given, much is expected. And there was little time to waste.

Despite the fact that human beings are 99.9 percent alike, according to the Human Genome Project, that 0.1 percent difference may yet drive mankind to annihilate the human race.

"There is tremendous militarism rising in response to what are clearly bad acts of terrorism," Sulston said. "But it is my belief that, in the end, the recourse has to be a balance of wealth. This is not to say that terrorists are always oppressed; frequently they are relatively rich. But the places they operate from, the causes they espouse and the support they get results from this imbalance of wealth and a lack of humanity nation to nation."

The work on the Human Genome Project is only the beginning of understanding how the human body works, Sulston said, and by the time the Banneker students graduate from college, the study of biology is sure to be more complex and more challenging.

But the findings of the genome project will always stand as a reminder of a common heritage among all human beings.

"We often neglect that which is common among us for that which is private and exclusive," Sulston said. "What we have in common is more precious than anything, for it is life itself, and we should cherish it."

The students listened intently, some with hands on their chins, thinking.

E-mail:milloyc@washpost.com