Evolution of DNA base composition under no-strand-bias conditions when the substitution rates are not constant.
The evolution of DNA base composition evolution is simplified to a six-parameter model when there are no strand biases for mutation and selection. We analyzed the dynamics of this model with special attention to the influence of a change in substitution rates. The G + C content of the DNA sequence tends to an equilibrium value that is controlled by four parameters of the model. When the substitution rates are not constant, the G + C equilibrium position is not constant. The DNA sequence base frequencies always tend to a state in which A = T and G = C within a strand, regardless of substitution rates. This is true even when the substitution rates are not constant over time. This provides a simple way of rejecting the model from inspection of present-day DNA base composition.
Lobry
J R
JR
Laboratoire BGBP-CNRS, Université Claude Bernard, Villeurbanne, France. lobry@biomserv.univ-lyon1.fr
Lobry
C
C
D001482:Base Composition; D003062:Codon / Q000235:genetics; D004247:DNA / Q000737:chemistry* / Q000235:genetics*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D019143:Evolution, Molecular; D008957:Models, Genetic; D009154:Mutation; D012641:Selection, Genetic
D003062:Codon; D004269:DNA, Bacterial; D004247:DNA