Computing with DNA.

1. A New Player in the History of Computation A brief look at the history of humanity shows that since the earliest days people needed to count and compute, either for measuring the months and the seasons or for commerce and construction. The means used for performing calculations were whatever was available, and thus progressed gradually from manual (digits) to mechanical (abacus, mechanical adding engine), and from there on to electronic devices. Electronic computers are only the latest in a long chain of human efforts to use the best technology available for performing computations. Although it is true that their appearance, some 50 years ago, has revolutionized computing, electronic computers mark neither the beginning nor the end of the history of computation. Indeed, even electronic computers have their limitations: There is a limit to the amount of data they can store, and physical laws dictate the speed thresholds they will soon reach. The most recent attempt to break down these barriers is to replace, once more, the tools for performing computations with biological ones instead of electrical ones. DNA computing (also sometimes referred to as biomolecular computing or molecular computing) is a new computational paradigm that employs (bio)molecule manipulation to solve computational problems, at the same time exploring natural processes as computational models. Research in this area began with an experiment by Leonard Adleman, who surprised the scientific community in 1994 (1) by using the tools of molecular biology to solve a difficult computational problem. Adleman's experiment solved an instance of the Directed Hamiltonian Path Problem solely by manipulating DNA strands. This marked the first solution of a mathematical problem by use of biology.