Figure 1. Network model and jitter.

(a) is a cartoon depicting the Drosophila circadian molecular network; protein and mRNA are represented by capital letters and lower case, respectively. Red arrows and cyan blocked lines indicate stimulatory and inhibitory interactions, respectively. The green arrow ending in X indicates that CRY protein enhances the degradation of TIM. (b) and (c) plot recurring orbits of the wt and cwo-mutant models in LD (cycles 100 to 120000), respectively; observe the jitter/variation when CWO is absent. The variability of CWO is proportional to the variability of each direct target gene at the times of its peak and trough (, see File S1):

(d) plots the variability of CWO (y-axis) vs. per mRNA (x-axis) at the peak-time of per. (e) illustrates the theoretical results predicting that the jitter of CWO dampens the jitter of direct targets at the times of their peaks and troughs. (f)–(k) plot per oscillations in simulations where the CLK/CYC of each cycle (total = 70) of the wt (f–h) and the cwo-mutant (i–k) models is pulsed at ZT = 14 hr by pseudorandom numbers drawn from a uniform distribution on [0, 0.001] (f and i), [0, 0.01] (g and j), and the unit interval (h and k), respectively. The unit of the y-axes of b–c and f–k is arbitrary.