The goal of being able to program biochemical reactions as precisely and easily as computers crunch numbers and process words has moved a giant step closer.

California Institute of Technology researchers have created a DNA-based fabricator that allows for specifying a piece of DNA with a desired shape and function; it then executes a molecular program to assemble it in a test tube.

To demonstrate the power and flexibility of their programming approach, the group used it to produce several different reactions including, most dramatically, two-legged DNA molecules that walk along a ladder-like track, modeled on the transport protein kinesin, which walks along microtubules at about 100 steps per second.