Now what about true viral surgery?" He was hitting his stride. I could imagine him strutting around in front of a university biology class, boring his students to death. "Say you're a diabetic, which means you can't-produce enough insulin, an enzyme normally produced by the pancreas. In such a case, your pancreas cells lack the genes to produce the enzyme. If we're limited to genetic engineering, we can create a bacterium that secretes insulin, then inject the insulin into your body daily, and we can make sure that any children you have don't inherit the trait. Not the best answer.