Figure 1.

Network diagram for the mathematical model of the Neurospora clock. The model incorporates the core genes frequency (frq) and white collar-1 (wc-1 ). The protein product of the wc-1 gene (WC-1) is the positive element of a central negative feedback loop, while the frq protein product (FRQ) is the negative element. FRQ also upregulates the level of WC-1 yielding a positive feedback loop interlocked with the primary one. WC1* represents light-activated WC-1. Thicker lines denote the delay between the translation of a protein and conversion into its active form, modelled using a distributed delay.