Modeling the Heterogeneity of Genomes

Strong variations of the G+C content in genomes of warm-blooded vertebrates ("isochores") have been observed a long time ago, but any explanation of their possible origin has remained out of reach. Here we present one possible mechanism that could explain the dynamic origin of isochores by using mutation patterns derived from the recently published human genome. The key element of the dynamic model is the strong G+C dependence of mutation rates. We show that the observed mutation patterns imply an unstable mutational equilibrium, and that deviations from equilibrium are amplified exponentially. In this way G+C rich regions become even richer, whereas G+C poor region become poorer.