Circadian clock, a biochemical mechanism that oscillates with a period of 24 hours (in accordance with the day-night cycle); driver of the circadian rhythm
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Using bacterial luciferase as a reporter for gene expression, studies have shown that, similar to Drosophila, mouse, and Neurospora clock models, the Synechococcus circadian clock is based on a negative feedback loop.
Frq- The Frq gene, also known as the Frequency gene, encodes central components of an oscillatory loop within the circadian clock in Neurospora.
In the mammallian circadian clock, for example, transcription factors CLOCK and BMAL1 are the positive regulators.
Clock- The clock gene in Drosophila encodes for the CLOCK protein and forms a heterodimer with the protein CYCLE in order to control the main oscillating activity of the circadian clock.
Pdf has also been studied in the cricket Gryllus bimaculatus; studies proved that Pdf is not necessary for generating the circadian rhythm, but involved in control of nocturnal behavior, entrainment, and the fine-tuning of the free-running period of the circadian clock.