Disparity mutagenesis model possesses the ability to realize both stable and rapid evolution in response to changing environments without altering mutation rates.

It has been shown that the disparity model, in which mutations are introduced exclusively in the lagging strand, has a great advantage in the promotion of evolution, compared with the conventional parity mutagenesis model. To understand much more about the characteristic of the disparity model, a novel 2-D genetic algorithm (GA) which reflected gene interactions was developed. The GA consisting of the lattice model showed powerful abilities to evolve. Even under conditions of high mutation rates with an extra genetic load, the GA could quickly evolve and finally attain a long stable state with high fitness scores. Arbitrary interruption of the stable state of evolution by various lengths of environmental stress could produce new individuals with different genotypes within relatively short periods and the mutants finally occupy the population; that brought back the picture of “punctuated equilibrium”. Interestingly, this phenomenon could be reproduced with certainty without changing mutation rates at all. As long as the fidelity difference between the lagging and leading strand was kept high enough, the robustness of the disparity model was very high. The acceleration or slowdown of evolution can be unambiguously introduced only by environmental changes, and the seesawing mutation rate is not the necessary condition for changing the speed of evolution.