Figure 6.

Semantic change without mutation of the genome. (a) Reactions. Key as in figure 4. (1) Mutation while expressing G0 leads to E1 instead of E0. The error is shown with a dashed red arrow. (2) E1 interprets G0 differently from E0. Where E0 reads G0 as coding for E0, E1 reads the gene as coding for E2. Thus E1 expresses E2 without error. (3) E2 interprets G0 as a specification for C0, P0 and E2. (b) System dynamics. Smoothed using Loess smoothing, and showing only the molecular species from the left panel. Timing of step 1 is shown with a red arrow. In this example, the genome (black), the copier machine (green) and payload (grey) all remain unchanged. The original expressor (blue) is replaced by a mis-expressed expressor (orange).