Science: The Perils of Treading on Heredity

The prospect is intoxicating. By mapping and manipulating tiny genes, man . could conceivably conquer diseases, improve upon his natural abilities and perhaps even control his own destiny. But just because miracles might someday be possible does not necessarily mean that they should all be performed. The tools of molecular biology have enormous potential for both good and evil. Lurking behind every genetic dream come true is a possible Brave New World nightmare. After all, it is the DNA of human beings that might be tampered with, not some string bean or laboratory mouse. To unlock the secrets hidden in the chromosomes of human cells is to open up a host of thorny legal, ethical, philosophical and religious issues, from invasion of privacy and discrimination to the question of who should play God with man's genes.

The opportunities and dilemmas created by the new genetic knowledge begin even before birth. It is already possible, through a variety of prenatal tests, to determine whether a child will be a boy or a girl, retarded or crippled, or the victim of some fatal genetic disorder. The question of what to do with that information runs squarely into the highly charged issue of abortion. Many could sympathize with a woman who chooses to terminate a pregnancy rather than have a baby doomed to a painful struggle with, say, Tay- Sachs disease or Duchenne muscular dystrophy. But what about the mother of three daughters who wants to hold out for a son? Or the couple that one day may be able to learn whether an unborn baby has a minor genetic blemish? Only the most hardened pro-choice advocate would argue that prospective parents have the right to abort fetus after fetus until they get the "perfect" baby.

Complicating such decisions is the fact that genetic prognostication will probably never be an exact science. Technicians may someday be able to determine that a fetus has a predisposition to heart disease, certain cancers, or a variety of psychiatric illnesses. But they will not be able to predict precisely when -- or even if -- the affliction will strike, how severe it will be and how long and good a life the baby can expect. As scientists learn to detect ever more minute imperfections in a strand of DNA, it will become increasingly difficult to distinguish between genetic abnormalities and normal human variability. "We haven't thought much about how to draw the line," admits Arthur Caplan, director of the Center for Biomedical Ethics at the University of Minnesota. "It is going to be one of the key ethical challenges of the 1990s."