Fig. 3

Summary of simulation results. a Examples of the resulting space–time plots from an individual at the end of a simulation. The posterior growth zone on the right is anchored and the other cells shift position when the tissue grows. The colour reflects the cell type, which is determined by the precise combination of expression levels of all genes within a cell. Note the regular alternation of gene expression in the posterior growth zone. b Left: a simplified representation of the gene regulatory networks that evolve in our simulations; right; an example of an evolved network (pruned, see "Methods"). The clock that generates gene expression oscillations is indicated in blue, the bistable switch in red. c Frequency profile of the segmentation gene (wave and constant frequency profiles) or the strongest oscillating gene (damped profile) in three simulations with a shallow gradient. d Snapshots of the tissue-level gene expression, corresponding to the profiles in c (blue is high expression, white is low). The anterior ends (indicated by the black bars) are aligned for greater clarity. The pictures are taken 12 steps apart