These fears and hopes have traveled with all kinds of work on the genome from Watson and Crick through the Asilomar Conference on Recombinant DNA to the earliest gene trials and the sequencing of the human genome. But until very recently, we had no evidence that transferring genes into human cells was helpful at all. In the early 2000s, gene therapy suffered a series of setbacks, including the high-profile death of a young patient. In the words of the Mayo Clinic, "The possibilities of gene therapy hold much promise. To date, however, that promise has not been realized."

Given that background, I was planning to write a story about how it was sort of nuts for John Leonard to talk about genetic manipulation, not because athletes wouldn't try it, but because it's unlikely to be effective.

But then I called up Richard Snyder, a University of Florida biologist who has a grant from the World Anti-Doping Agency to create reliable blood tests for gene doping. As as result, he's intimately involved in both what might be possible with current gene transfer technology -- and how we might detect any kind of illicit practice.

Snyder told me that gene doping of exactly the kind you'd expect high-level athletes to use is already effective in animals and that in the last few years, therapeutic gene therapies in humans have started to experience and sustain success, particularly in treating hemophilia and certain types of congenital blindness. And right now, there's no available test for gene doping. Put those three facts together and the idea that someone might be transferring genes into his or her body doesn't sound so outlandish.

"In the last five years, there have really been some dramatic examples of gene transfer being efficacious in humans. What we've been seeing in animals for a long time is coming to humans. We've optimized the delivery routes and the viral gene transfer vectors themselves. We understand the diseases better and know what genes we need to deliver to treat people," Snyder said. "This technology can also be usurped for illegitimate means."

He sent me over a paper his team published last year in the journal Gene Therapy, and began to walk me through how gene doping -- and his method of catching it -- could work.

How Gene Doping Works



Here is the basic idea of gene doping. First, you need a virus. Viruses work by going into the cells of your body and hijacking the machinery in there to make more of whatever they want, which in many cases is more viruses.

Second, you need to modify that virus. Scientists have been defanging viruses for a while and turning them into DNA delivery machines that they call vectors. These viruses are loaded with a "cassette" (this is actually what they call it) of DNA that the viruses then insert into cells within the mammalian body.