Knockout Mice

The ability to remove or alter with precision a single one of the thousands of genes in the body and to transmit this mutation to all subsequent progeny was a science-fiction dream only a few years ago. But today this technique is part of a routine procedure for creating animal models that can be used to study the pathophysiology and therapy of diseases in humans. In general, mutations that cause a gain of function produce disease even when they occur in only one of a gene's two alleles; for example, the oncogenic mutations that cause abnormal cell proliferation. In a . . .