More seriously, the Caltech researchers used DNA molecules to build their artificial neural network (which is the beginnings of a brain) because they can act like circuits, computing data, transmitting information and processing it. Discovery explains:
Without getting too complicated, Qian and her team created four highly simplified artificial neurons in test tubes comprised of 112 strands of DNA, each strand programmed with a specific sequence of bases to interact with other strands. The interactions resulted in outputs (or not), basically mimicking the actions of neurons firing. In order to see the DNA neurons firing, the scientists attached a fluorescent molecular marker that lit up when activated.
They tested the artificial brain by quizzing it with DNA strands that hinted at an answer. Using clues from the strands, the artificial neural network answered correctly every time. Read more of this fascinating experiment at Discovery. [Laboratory Journal via Discovery]