You walk into your doctor's office and are told that you carry the gene for liver cancer. You probably won't develop the disease for another 30 years, but now you know how you will probably die.

Or you walk into your obstetrician's office and are told the fetus you are carrying has the gene for cystic fibrosis. And the genetic profiles collected from you and your husband have also revealed another startling fact: Your husband is not the father.

Or you cannot get health insurance because you carry the gene for coronary artery disease, and the company does not want to pay for your care.

These scenarios are not as far-fetched as they might seem, according to a group of experts in medicine, law and ethics who met last week in Bethesda to examine the social implications of identifying all the genes in the human body. The meeting was sponsored by the National Center for Human Genome Research, the international project designed to map the precise location for each of the 50,000 genes that make up the full human complement.

Housed at the National Institutes of Health, the genome center has set aside 3 percent of its annual budget to study the ethical, legal and social impact of such unprecedented knowledge about human genes. The project's total budget has been estimated at $3 billion over the next 15 years, of which $140 million was appropriated for the current fiscal year.

Among the thousands of human genes, all strung like beads in a standard arrangement along 46 chromosomes, each person probably carries hundreds that deviate from the norm in some inconsequential way. Also included are a few -- probably no more than 10 -- that would be deadly if a person had them in a double dose, one from each parent. The personalized genetic blueprint that will be available early in the next century will uncover each one of those flaws, the harmless as well as the dangerous.

When the full human genome -- the collective name for all human genes -- is mapped, "we risk greatly expanding the numbers of people who do not fit our definitions of normal, able and healthy," warned Judith Swazey, president of the Acadia Institute in Bar Harbor, Maine. Significantly, not all of those people will be functionally ill.

"What exactly is an abnormality?" asked Arthur Caplan, director of the Bio-Medical Ethics Center at the University of Minnesota. "Is any abnormality a disease?" He said there is already a precedent for defining deviations from the statistical norm as "disease," such as high blood pressure, high cholesterol and obesity.

As knowledge of the genetic map increases, physicians may be able to pinpoint "abnormal" in more precise ways. Then, the experts said, people will encounter what Swazey called "the lay public's 'monster mythology' fears" of how such knowledge can be turned against them.

Among those fears:

Genetic discrimination. People with genetic flaws, not all of which show up as dysfunctions, may nonetheless be denied life insurance, health insurance, access to schooling, or jobs.

Differential treatment. Employers, for instance, may selectively hire only those people whose genes indicate they are resistant to the health hazards of the workplace, which is a cheaper alternative than cleaning up the workplace to make it safe for everyone.

Eugenics. Social or political pressure may be applied to people to make childbearing decisions on the basis of genetic information. Mating between those with valued genes may be encouraged; mating between two people with dangerous recessive traits may be prohibited; women shown to be carrying fetuses with genetic abnormalities may be forced to abort.

All the "monster myths," even those that seem outlandish, have precedents in current practice, the experts pointed out. For instance, laws prohibiting marriages between close relatives are a form of "negative eugenics," an attempt to avoid genetic problems in offspring -- a risk that is increased when relatives marry.

"I think genetic diseases could become a new form of contagious disease," said Leonard Glantz, professor of health law at Boston University. Public health officials, he said, might consider it their job to control the spread of "bad genes," just as they currently try to control the spread of infectious bacteria and viruses.

And ways to control the spread of bad genes include mass genetic screening, forced genetic therapy, and possibly efforts to forbid people with certain genes to bear children. Genetic counselors, who now just lay out risks and options for prospective parents, might also feel justified in being more authoritarian in their advice. All of these prospects worried the conference participants.

The experts also expressed concern that new genetic discoveries could fuel the notion of "genetic determinism" -- the belief that behavioral and personality characteristics, such as intelligence or criminality, are predominantly a function of genes.

Genetic determinism is already used to justify bigotry, said Patricia King, a professor at the Georgetown University Law Center. Once the entire genome is mapped, she said, genetic differences that can be collected according to race could be further misused to perpetuate racial or ethnic inequities.

"Whenever you hook up genes and race," she said, "the message is clear in America: African-Americans suffer."

Genetic determinism implies a fatalistic attitude toward health and disease, added Eric Lander, a molecular biologist at the Whitehead Institute of the Massachusetts Institute of Technology. "People seem to think that if it's genetic, it's unchangeable," he said. "That's pernicious nonsense."

Even some purely genetic conditions can be influenced by the environment, Lander pointed out. Phenylketonuria (PKU), for instance, is an inherited metabolic defect that causes mental retardation. But if it is detected at birth and the affected child is kept on a special diet, the PKU gene has no effect on mental development.

"So here you have a condition that's 100 percent genetic on the one hand," he said, "and 100 percent environmental on the other."

The goal of the two-day meeting was to raise troubling questions, not to answer them.

Among the questions that panelists considered:

Once it becomes possible to test quickly and reliably for thousands of genetic conditions, will every physician be expected to perform such tests? Will he or she be liable for malpractice for failing to do so, or for failing to tell patients every detail of the test results?

Who should counsel patients about what their genetic blueprints mean? Will people eventually be handed a computerized read-out and be offered little in the way of explanation? How will they react to information about their particular genetic makeups?

Will health insurers deny policies to people with genes for diseases with a high economic cost? Will life insurers? Does either have the right to do so?

How can genetic profiles be kept confidential? How can discriminatory use of test results be prevented? Since some of these tests will reveal information not only about the individual tested but also about family members, can the relatives' privacy be protected?

Do people have the right to choose not to know about their genes? Do mothers have the right to choose not to have their fetuses tested?

The meeting coordinators -- George J. Annas, professor of health law at Boston University, and Sherman Elias, director of reproductive genetics at the University of Tennessee in Memphis -- will present these questions to the human genome center and make recommendations about directions for research into the social implications of genetic discoveries.

Similar conferences are scheduled over the next six months around the country, including two more in the Washington area.