The biologists fear the new technique is so effective and easy to use that some physicians may push ahead with it before its safety can be assessed. They also want the public to understand the ethical issues surrounding the technique, which could be used to cure genetic diseases, but also to enhance qualities such as beauty or intelligence. The latter is a path that many ethicists believe should never be taken. “You could exert control over human heredity with this technique, and that is why we are raising the issue,” said David Baltimore, a former president of the California Institute...