Flexible DNA Computer Finds Square Roots - Science News: The basic design incorporates two types of synthetic DNA in a test tube: single-stranded DNA molecules that float free like lone wolves and double-stranded ones that carry a small notch of open DNA called a “toehold.” The single-stranded DNA cruises solo until bumping into an entwined pair of DNA strands with a matching toehold. The lone wolves anchor onto that toehold by zipping, eventually booting off one of the original two strands. After the zipping and unzipping is done, a new double-stranded molecule and single-stranded lone wolf float around the test tube.
By precisely designing these DNA cascades, the team could squirt molecules representing 1001 in binary notation, or 9, into the mix and isolate a binary answer once the resulting reactions finished. In this case, that answer was a square root: binary 11, or 3. But the cascades, like the model trains, are customizable, and the team could have easily designed a circuit to do addition or subtraction instead. “It’s the simplicity that enables the complexity,” says Winfree, a bioengineer.