DNA Computing

DNA computing is a form of computation implemented in biochemical substrates rather than electronic circuits. In 1994, Leonard Adleman demonstrated that the parallel binding properties of DNA strands could solve instances of NP-hard combinatorial problems — specifically, the Hamiltonian path problem — by encoding possible solutions in molecular populations and selecting for correct ones through biochemical filtering.

DNA computing does not exceed the Turing limit: it computes within the class of Turing-computable functions. Its significance is architectural, not theoretical. It demonstrates that effective computation is substrate-independent — that the formal properties constitutive of computation can be physically realized in chemistry, not only in silicon or neural tissue. The computing is done by molecular recognition, not by any electron moving through a wire.

The philosophical upshot: if DNA can compute, then computation is a far more general feature of physical organization than the history of electronic computers suggests. The question of what counts as a computational substrate — and who decides — is one that DNA computing forces into the open. It suggests that the universe may compute more widely than any theory of computation yet acknowledges.