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DNA Tic-Tac-Toe
By Kate Dalke

Scientists have created a device that uses DNA to play a competitive game of tic-tac-toe. The device never makes a mistake, either beating its human opponent or forcing a draw every time.

It’s not just all fun and games. The researchers show that biological molecules like DNA and enzymes can be built to act like electrical circuits.

Someday, these biological circuits could be used to, say, make sensors in cells that would know when to release drugs inside the body.

Why use DNA to play the game? Nothing else has the flexibility to recognize and respond to thousands of different molecules, says Milan N. Stojanovic of Columbia University in New York.

Stojanovic and Darko Stefanovic of the University of New Mexico developed the device, which is called MAYA.

MAYA is made up of nine wells in a plastic dish that correspond to the three-by-three grid of tic-tac-toe. Each well contains a different solution of enzymes.

MAYA always begins by making its move in the center well—the optimal first move in tic-tac-toe.

Instead of using an X or O to mark the spot, the human player designates his or her move by choosing a strand of DNA that corresponds to a specific well. The person adds the DNA to each well, but only the chosen well lights up to indicate the move.

MAYA then responds by lighting up another well on the board, making its optimal move to block or win. This continues until the device wins, or there is a draw.

In over 100 games, the device never made an incorrect move. This is the first time that biomolecules have been assembled in such a way that they can “autonomously play a dynamic game,” the scientists say in Nature Biotechnology.

Tic-tac-toe is one of the oldest recorded games and has been a favorite for testing new computer devices. The first game coded on an electronic computer was tic-tac-toe on the EDSAC in 1949.

“It’s advanced science with fundamentals that can be understood by many,” says Stojanovic.


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Stojanovic, Milan N. and Darko Stefanovic. A deoxyribozyme-based molecular automaton. Nat Biotechnol. Published online August 17, 2003.

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