MarkvW said:
Gene therapy is really Dr. Frankenstein (that's Frahnk-N-Steen) stuff. This stuff isn't transitory. It creates permanent results; results that are passed through to offspring.
There are two kinds of gene therapy. The more common kind, which is being done RIGHT NOW, introduces the foreign gene into somatic tissues, and is NOT passed along to offspring. This is approved in certain clinical trials and is already having major medical benefits. To take just one example, people with coronary artery problems can be given gene therapy that results in the growth of new blood vessels to the heart. Needless to say, this would very likely result in performance enhancement.
The other kind of therapy, which has not been approved, and which most people in the field believe should never be approved, introduces the foreign gene into germ cells, eggs or sperm. This type of therapy is passed along to your kids.
Finally, gene therapy of either kind is not necessarily permanent. One can build into the gene a mechanism that allows the gene to be turned on or off. Also, as another poster mentioned or alluded to, at the current state of the art, the foreign gene gets degraded or eliminated from the body's cells eventually. Future developments will probably greatly extend its time of action, though.