A quantum mechanical model of adaptive mutation

The principle that mutations occur randomly with respect to the direction o f evolutionary change has been challenged by the phenomenon of adaptive mut ations. There is currently no entirely satisfactory theory to account for h ow a cell can selectively mutate certain genes in response to environmental signals. However, spontaneous mutations are initiated by quantum events su ch as the shift of a single proton (hydrogen atom) from one site to an adja cent one. We consider here the wave function describing the quantum state o f the genome as being in a coherent linear superposition of states describi ng both the shifted and unshifted protons. Quantum coherence will be destro yed by the process of decoherence in which the quantum state of the genome becomes correlated (entangled) with its surroundings. Using a very simple m odel we estimate the decoherence times for protons within DNA and demonstra te that quantum coherence may be maintained for biological time-scales. Int eraction of the coherent genome wave function with environments containing utilisable substrate will induce rapid decoherence and thereby destroy the superposition of mutant and non-mutant states. We show that this accelerate d rate of decoherence may significantly increase the rate of production of the mutated state. (C) 1999 Elsevier Science Ireland Ltd. All rights reserv ed.