FIG 6.

The nsp12-V553I mutation is stable across passages; however, nsp12-M611F is vulnerable to reversion. DBT cells were infected at an initial MOI of 0.01 and then blind passaged in triplicate for 5 passages. Total RNA was taken, and sequencing was performed across a 1.7-kb region of nsp12-RdRp that included both mutations. The percentage of each nucleotide present in each of the triplicate lineages after 5 passages is shown. Mutant viruses in the WT and nsp14-ExoN(−) backgrounds are shown. The original mutation for each of the viruses is shown above the graph, and the likely majority, secondary and tertiary codons present in the population are shown below the graph.