Angela knew that given her family history, there was a strong likelihood a genetic mutation was being passed from one generation to the next. But testing positive would mean she'd have to make some very difficult decisions. To begin with, having a BRCA mutation doesn't guarantee a woman will get cancer. It only increases the likelihood. And the options currently available to a BRCA carrier are at best rather limited, and at worst strikingly unappealing. Once a women is identified as high-risk, her clearest strategy is vigilance; she can maintain a rigid program of regular examinations so that if a cancer develops, it can be found and treated early.

The newest avenue being pursued is what's referred to as chemo-prevention. That is using the drugs Tamoxifen and Raloxifene in high-risk women before the onset of disease. The problem here is the potential for substantial side effects. Tamoxifen, for example, is believed to greatly increase a woman's risk of uterine cancer over time.

There are two far more extreme strategies as well. One is to have a preventative oophorectomy, which is the surgical removal of the ovaries. Because the current screening techniques for early-stage ovarian cancer are not especially effective, an oophorectomy is an option some women -- particularly those who've already had kids -- consider seriously. Even more radical is a preemptive mastectomy, which is a far more complicated and psychologically loaded choice. (In the past year, about 50 of these kinds of oophorectomies, and five mastectomies, have been done at Sloan-Kettering.)

Genetic testing is one of the first tangible benefits of the golden age of biotechnology. It's easy to forget that it was only twenty years ago that researchers even began to examine the notion of cancer as a genetic disease. Opening the window wider and wider on the way genes work, and fail, will -- like Darwin's theory of natural selection and Einstein's quantum physics -- change the way we look at the world.

But this new era is fraught with frightening issues, questions that would have been unimaginable just ten years ago. And while progress is taking place at the speed of light, the science can still seem painfully inadequate, particularly for someone at risk. If genetic testing for breast and ovarian cancer can predict only probabilities, not certainties, and if the treatment options are severely limited anyway, what's the point? Particularly when you think about the potential psychological impact of telling a woman she's a walking biological time bomb.

Not to mention the enormously complicated family issues, the potential for insurance-company discrimination, and the further potential for discrimination against particular racial or ethnic groups that show a genetic propensity for certain maladies.

For many people, none of these issues is as disturbing as the fact that the entire idea of genetic testing strikes them as some haunting scientific remnant of the Third Reich. For some time, the search for the causes of cancer has focused on external factors: the environment, pesticides, carcinogens in food, tobacco. But now it's possible to say the cause is actually within the individual; in fact, it's in our DNA, the very essence of what makes us who we are. Eugenics, then, hardly seems out of the question.

"We are on the verge of being able to map the entire human genome," says Dr. Harold Freeman, the director of surgery at Harlem Hospital, referring to the fact that the National Institutes of Health and several private companies believe that by 2003 they will have identified every one of the 100,000 or so genes in the human body. "This is a scientific achievement that's the equivalent of splitting the atom. It's powerful knowledge, and we can use it to create a bomb or we can use it to create energy and help people," cautions Freeman, who's also the chairman of the President's Cancer Panel.