Assignment of circadian function for the Neurospora clock gene frequency

Circadian clocks consist of three elements: entrainment pathways (inputs), the mechanism generating the rhthmicity (oscillator), and the output pathwa ys that control the circadian rhythms. It is difficult to assign molecular clock components to any one of these elements. Experiments show that inputs can be circadianly regulated(1-3) and outputs can feed back on the oscilla tor(4,5), Mathematical simulations indicate that under- or overexpression o f a gene product can result in arrhythmicity, whether the protein is part o f the oscillator or substantially Dart of a rhythmically expressed input pa thway(6). To distinguish between these two possibilities, we used tradition al circadian entrainment protocols(7,8) on a genetic model system, Neurospo ra crassa.