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Nature Structural & Molecular Biology 15, 23–24 (1 January 2008) | doi:10.1038/nsmb0108-23

The intelligent clock and the Rube Goldberg clock

Aziz Sancar

Circadian rhythms are generated by cell-autonomous molecular clocks in organisms ranging from cyanobacteria to humans. Recent research on the mechanisms of molecular clocks call for a reflection on the cause and necessity of complexity in biological systems. Circadian rhythm is the change in physiology and behavior of organisms with a periodicity of about 24 hours. The rhythm is generated by a cell-autonomous molecular clock.