Fig 2.
Cascaded gene circuits. (a) Schematic representation of a two-gene cascade where the expression of the second gene is positively regulated by the concentration of the first protein such that kR2 = kRmax2/[1 + (kd2/p1)n]. The first gene circuit is negatively autoregulated as described in Fig. 1b. (b) Graphical representation of the change in the p1 noise PSD caused by feedback in the p1 circuit. If properly filtered by the second gene circuit in the cascade, the noise between the unregulated and regulated noise bandwidths may be rejected.