Figure 3.

The relationship between the true and observed numbers of mutations and variable sites in a lineage. For each intermediate, the percentage of observed nucleotide substitutions with respect to R67 is given on the abscissa. On the ordinate are the true percentages of forward, back, and total mutations in the lineage to the intermediate sequence as well as the true percentage of variable sites. Whether it be any of these variables, there was a linear relationship with those numbers computed by simply comparing any intermediate sequence to the R67 reference—i.e., by ignoring the lineage.