Here is an interesting article from Science News about applying on/off switches to DNA-able structures. It's really funny. Back in the 50's and all the way up till the 80's scientists seemed to think that we'd all be flying to school on hoverbelts, driving our rocket cars into orbit for lunch, and carrying frickin' laser beams around like George Jetson by now. Instead we got cloned sheep, genetic mapping, and Big Brother.
Hey, at least Orwell was right. Somehow, I wish Heinlein had been instead.