On January 17, 2022, Brian R. Morton, professor of biological sciences, published new research in the Journal of Molecular Evolution, titled “Context-Dependent Substitution Dynamics in Plastid DNA Across a Wide Range of Taxonomic Groups.” In this paper, Professor Morton compares angiosperms, gymnosperms, ferns, liverworts, chlorophytes, stramenopiles, and rhodophytes to evaluate the influence of context on substitution bias at fourfold degenerate coding sites and in intergenic regions in plastid DNA.
He found context effects in all lineages and, despite this, observed significant differences between lineages. The research also demonstrates that even though there are similar effects of context on substitution bias at fourfold degenerate coding sites and within intergenic regions, there are small but significant differences. This suggests natural selection’s action at some of these sites and possible differences in the mutation and/or repair process between coding and noncoding DNA.