  How mutations accumulate in genomes is the central question of molecular
evolution theories, however our understanding of this process is far from
complete. Drake's rule is a notoriously universal property of genomes from
microbes to mammals - the number of (functional) mutations per-genome
per-generation is approximately constant within a phylum, despite orders of
magnitude differences in genome sizes and diverse populations properties. So
far there is no concise explanation for this phenomenon. A formal model of
storage of genetic information suggests that a genome of any species operates
near its maximum informational storage capacity, and the mutation rate is near
its upper limit, providing a simple explanation for the rule with minimal
assumptions.
