Figure 5. Model predictions and analysis of repression cascades.

(a) Simulations of time to half-maximal response using the model. Increasingly layered cascades show a positive linear relationship between circuit time to half-maximal response and circuit depth, with a slope of 184.9±0.2 (s.e.m.) min layer⁻¹. The first four data points highlighted in purple are experimental data from Fig. 4b. (b) Signal degradation, δ, in a cascade increases as transcriptional leak of the gates increase. Boxplots of δ values were plotted with binned values of the leak parameter L. At values of L <1.75% the spread of performance of the cascades is significantly larger. The bin containing the steady-state experimentally predicted value of dCas9-Mxi1, L=0.6±0.1% (s.d.), is highlighted in purple. The bins highlighted in orange and yellow contain the predicted L values for the steric repression measurements in Fig. 2 of position 1, L=25.0%, and position 3, L=61.3%, respectively.