The strides now being made in genetic medicine presage a revolution in health care. Already, it is possible to determine a patient’s susceptibility to certain hereditary diseases. Within a decade, genetic tests will indicate who will respond well to a drug, who will barely respond, and who will suffer adverse reactions. Physicians will then be able to tailor therapies to the needs of individual patients.

Significant scientific and technical challenges remain, however. To date, scientists have identified the function and location of only a small fraction of the genes that define the human race. And every gene displays a number of variations—a phenomenon called polymorphism. Much more genetic data will thus have to be collected and deciphered before genetic medicine can reach its full potential. Moreover, testing patients to identify their genes is still a slow and expensive process that costs from $1,000 to $2,000 for each test, though a few simple tests for infectious diseases cost as little as $20.¹ The cost of individualized drug therapy, too, is likely to be high. And there are challenges in the realm of policy: what are the privacy rights of people who give genetic information to scientists and clinicians, for...