Dependence of k
Noise Response on Other Parameters. The qualitative nature of our results are independent of choice of parameter, although the quantitative measures do change. All panels show the fano factor (variance divided by mean) for varying values of k
holding all other parameters constant (a very similar pattern would be seen using coefficient of variation and/or controlling for constant protein expression). Importantly, the mathematical formulae only fit the simulations for weak k
, and the noise increases for strong repressors. (a) A less stable protein with γ
= 2 × 10-3s-1 exhibits similar behaviour; all other parameters are as in Figure 1(a). (b) A very stable protein with γ
= 2 × 10-5s-1 exhibits the same behaviour, except that with these parameters, the increase in fano factor never matches the noise of the unregulated system. (c) A more stable mRNA with γ
= 10-3s-1. (d) A cooperatively binding protein with Hill coefficient of 2 also shows the same pattern, but this time the noise is greater than the unregulated system for weaker repressors than in the non-cooperative case.