Clocks go forward: progress in the molecular genetic analysis of rhythmic behaviour.

The molecular basis of circadian homeostasis has proven to be amenable to genetic dissection in many model organisms. Surprisingly, additional factors contributing to an organism's "chronotype" continue to be identified using both forward and reverse genetics. As more factors are identified, the importance of rhythm regulation in all body systems is becoming apparent. Moreover, recent evidence confirms that the regulation of circadian homeostasis can be fine-tuned at a number of molecular levels. This not only ensures that biological rhythms are maintained at a robust level in all cells but also allows for the precise and rapid readjustment of rhythms in response to environmental factors.