Simulated expression profiles of the 101 gap gene circuits at the final time points. The x-axis corresponds to 35-92% of the A-P position and the y-axis describes the expression level in fluorescence units. The experimentally measured expression profiles are plotted with coloured dashed lines. They represent average quantitative gene expression data obtained from fluorescent immunohistochemistry stained Drosophila blastoderm embryos  followed by successive image-processing operations [46, 96]. The simulated profiles obtained from different circuits for each gene are shown in light grey and the average profiles at a specific time point are plotted using coloured solid lines.