Figure 4.

Simplified schematic of mutations accumulation in virus population. Mutations are identified by comparing a sequence of a viral isolate with a reference sequence (RefSeq). Individual positions where bases are mutated in at least one isolate are shown by rectangles. Blue rectangles are positions same as in RefSeq. g0—A genome of virus quasispecies starting a population that may already have some differences from RefSeq. g1—g9 rounds of replication generating additional mutations, which are numbered same as the generation in which a mutation event had occurred. Mutations occurring in later generations would be present in smaller fractions (reflected by the decreasing yellow color density) within the population. The entire set of independent mutation events would be described by the list in which every mutation is represented only once, regardless of the number of genomes where it is found. In this population, such a list is represented by the g9 genome.