Macdonald and her associates showcased the computer's potential by engaging MAYA-II in a complete game of tic-tac-toe against human opponents, winning every time except in the rare event of a tie. Shown in the foreground of the picture above is a cell-culture plate containing pieces of DNA that code for possible "moves"; a display screen (background) shows that the computer (red squares) has won the game against its human opponent (blue).
Composed of more than 100 DNA circuits, MAYA-II is quadruple the size of its predecessor, MAYA-I, a similar DNA-based computer developed by the research team three-years ago.
The computer always makes the first move by activating the center well. Instead of using buttons or joysticks, a human player makes a "move" by adding a DNA sequence corresponding to their move in the eight remaining wells. The well chosen for the move by the human player responds by fluorescing green, indicating a match to the player's DNA input. The move also triggers the computer to make a strategic counter-move in one of the remaining wells, which fluoresces red. The game play continues until the computer eventually wins, as it is pre-programmed to do, Macdonald says. Each move takes about 30 minutes, she says.