Most maps can tell you where you are and which way to go; gene maps can tell you which way you'll probably die. The question is, do you really want to know?
For the price of a Rand McNally World Atlas, you will soon be able to learn what your body has in store for you. A few drops of blood, a whirl in a centrifuge and the right enzyme cocktail are the necessary ingredients to cut and paste your double helix into a detailed map of the body's design. These maps reveal where the design may be ruinously flawed.
Genetic cartographers already chart genes for potential parents worried about passing on such diseases as Tay-Sachs and sickle-cell anemia to their offspring. But what of individuals who have already inherited their genetic time bombs? This is emerging as the new focus of this diagnostic technology. Gene markers can determine with near certainty whether an individual has inherited specific illnesses--most notably, Huntington's chorea, a particularly debilitating way to die--decades before any symptoms appear. As scientists map the new world of the human genome, we'll be hearing monthly announcements from researchers around the world trumpeting their latest discoveries of gene-linked disease--for example, the recent discovery of the gene for cystic fibrosis.
"The people who are doing research are quite right to say that new markers will be identified," says Dr. Neil A. Holtzman, a professor of pediatrics and epidemiology at Johns Hopkins who has written extensively on genetic testing. "These markers will give us tremendous new insights into the genetic makeup of disease."
The potential list is both awesome and depressing. Colon cancers, lung cancers and breast cancers? Almost certainly. Cardiovascular illness? High probability. Mental illnesses such as manic depression and schizophrenia? Quite likely. Alzheimer's? Possibly. These may well be diseases you will inherit no matter what you do. There are no preventive measures.
Then again, says Holtzman, gene maps may chart probability, not destiny. The map may reveal a 40% probability that you'll get pancreatic cancer or an 80% chance for cancer of the uterus. If you're lucky, you'll live longer. On the other hand, you may be able to escape your genetic susceptibility by managing your life style better: Stop smoking, eat more vegetables and the statistics that indicate your genetic propensity for a heart attack could drop to 3 in 10 from 8 in 10.
"We will clearly know how to detect those genetic predispositions," says Holtzman, "and this will worry some people to death. Unfortunately, we will have the ability to predict long before the ability to intervene. While physicians are accustomed to treating people with an overt disease, they really aren't prepared to sit down with someone and discuss probabilities. Physicians may have to be retooled to deal with this."
But, given the chance, do people really want to know their odds? In the case of Huntington's chorea, fewer than half of the hundreds of people eligible for the test chose to take it. They didn't want to know. (Similarly, most people in high-risk AIDS categories decline to be tested.) The pain of ambiguity is easier to handle than the risk of certainty.
"The need for intense counseling is quite extreme," says Nancy S. Wexler, president of the Santa Monica-based Hereditary Disease Foundation. "There's this fantasy that a lot of these people have that knowing would resolve a lot of problems in their relationships. But even if Huntington's goes away as an issue, they will still have their problems."
Huntington's chorea is an extreme case. But how would one's life change given the knowledge of how you are most likely to die? Will the proliferation of this new technology augur in a new era of fatalism? How will this explosion of personal knowledge change our most intimate relationships?
Should a fiancee insist on seeing a gene map before signing the prenuptial agreement? What happens to a marriage when the gene map says the husband has a 90% chance of having a crippling stroke in the next five years? Or that the wife will have a fatal leukemia?
Is getting a gene map of your 5-year-old the best thing to do? What if the child's map proves bleak? When do you tell him? Wexler tells of one Huntington's couple that gave marker data to one child but not to another because "they didn't think he could handle it."
What if one tests positive? Is every single twinge and ache interpreted as the onset of the crippling disease? The ready availability of this technology may create a painful new self-consciousness about human frailty and mortality.
On the other hand, millions of smokers blithely puff away with nary a care about the possible consequences. Maybe all this gene-linked data will be more numbing than enlightening, further desensitizing an already stressed-out population.
But what's most likely, I think, is a tremendous surge in the number of support groups such as Alcoholics Anonymous and the social network of AIDS volunteers, a flocking to religion and a dramatic rise in the counseling business.
"What you're talking about is astronomical," says John Fletcher, an Episcopalian minister and bioethicist with the University of Virginia School of Medicine. "What you're going to see is a lot of entrepreneurial activity in new screening and counseling services. We're not yet ready for the explosion that gene mapping is going to bring."