We often say you can make logic gates out of nearly anything. [Steve Mould] would agree as he just finished playing naughts and crosses (tic tac toe if you are an American) with a tray full of DNA. You can see the resulting game and how it works in the video below.
The use of DNA isn’t really significant as it simply implements a logic equation for each of the nine cells. So, for example, each cell is taken by an X (the DNA) only when certain other squares have been taken by O or not taken by O. So you essentially create an AND/OR gate using the state of each cell and its inverse.
Of course, the key is how do you input your moves and how does the DNA process the equations? The input is simple. You add a different solution for each move and turn to each cell. The processing requires a little lab work as explained in the video.
Honestly, this reminded us of a diode logic project from 1976. It seems like a program, but really it is just a clever use of combinatorial logic. Practical? Maybe not, but it is illustrative of how things are different in the biochemical world. And as we always say, practically anything can be a logic gate. Really.