Differential Gene Survival under Asymmetric Directional Mutational Pressure

We have simulated, using Monte Carlo methods, the survival of prokaryotic genes under directional mutational pressure. We have found that the whole pool of genes located on the leading DNA strand differs from that located on the lagging DNA strand and from the subclass of genes coding for ribosomal proteins. The best strategy for most of the non-ribosomal genes is to change the direction of the mutational pressure from time to time or to stay at their recent position. Genes coding for ribosomal proteins do not profit to such an extent from switching the directional pressure which seems to explain their extremely conserved positions on the prokaryotic chromosomes.