Figure 7.

Noise statistics of the gene network. Dependence of the Fano factor (a) and of the coefficient of variation squared (b) of the protein fluctuations on the rate of transcription k₀, according to the ssLNA (solid lines) and the hLNA (dashed lines). The noise measures are calculated for three values of the bimolecular constant k₃=1(yellow), k₃=0.1(purple), k₃=0.01(blue). All other parameters are given by $\left[G_T\right]=0.01$, $\left[E_T\right]=1$, k₁=10⁻⁵, k₂=100, k₋₁=k₋₂=k₋₃=10, k₄=k_s=k_dM=1. Stochastic simulations of the full networks (solid circles) and of the coarse-grained network (open circles) using the CME and the heuristic CME, respectively, were performed for a volume of Ω=100. Note that at this volume there is one gene and 100 enzyme molecules. Note also that the chosen parameters guarantee timescale separation (validity of the deterministic QSSA) and cooperative behavior in the feedback loop (see Figure 8)