Figure 6
From: Phenotypic error threshold; additivity and epistasis in RNA evolution
Comparison between additivity and epistasis in RNA folding (a) The relative probability of neutral replication under the additive assumption (λd) is plotted against the number of base substitutions (d), where the probability of neutral replication with epistasis (i.e. the fraction of neutral mutants observed in the yeast tRNAphe folding) is set to be 1 for each d as a reference. It can be seen that the effect of epistasis on the probability of neutral replication becomes larger as the number of substitution (d) increases. The same data as that of Fig. 5 are used. (b) The solid line (the left y-axis) represents the relative effective replication accuracy (Q e ) under the additive assumption plotted against the error rate (1 - q), where Q e calculated with epistasis is set to be 1 as reference (see Methods section – Probabilistic approach – for details). It can be seen that the effect of epistasis on Q e increases as the error rate (1 - q) increases. The shape of the curve is in a similar manner as that of the curve in Fig 6a. Although the x-axis of Fig 6b is different from that of Fig 6a, one can relate the two graphs via the average d per neutral replication, with which the different x-axes can be transformed to each other. The average d per neutral replication is represented by the dashed line (the right y-axis plotted against 1 - q). Its value is calculated under the additive assumption as d = Np/(q + p) where p = λ (1 - q), λ = 0.4 and N = 76.