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

Abstract

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.

A differential equation, deduced from a DNA-type genetic algorithm with the lagging-strand-biased mutagenesis

“…This model GNA is expressed as (FC=50, JK=200). The details of the contents of the GA and conditions for simulations were described in the-previous study [15] .…”

“…In our previous report [15] we regarded DNA as a sequence of connected genes on a two-dimensional information lattice and assumed that neighboring genes interacted with each other.…”

“…In the previous report [15] , the simulation was performed under the following conditions. The mutation rate of the lagging strand was an integer and was normally distributed around Pa (mutation rate of lagging strand).…”

“…The GA used in the present study was basically the same one as previously published, which was the 2-D DNA-type GA [15] . This digital DNA takes into consideration gene-to-gene interactions and semi-conservative replication using a leading and lagging strand according to the DNA of living things.…”

The Inherent Asymmetry of DNA Replication

“…This type of strand-based mutational imbalance was termed disparity mutagenesis by researchers studying evolutionary adaptations, and was initially proposed as a mechanism to allow organisms to achieve a high mutational load without severely compromising an organism’s fitness through loss of genome stability (Fujihara and Furusawa, 2016). The evolutionary logic of disparity mutagenesis is as follows: A majority of random mutations are concentrated upon the lagging strand as a result of discontinuous lagging-strand synthesis.…”