Circadian clock and microarrays: mammalian genome gets rhythm

Circadian (daily) rhythms are found in most living organisms from cyanobacteria to mammals. They are generated by an internal 'clock'that is reset by external time cues and that regulates a variety of physiological functions through downstream target genes. Analysis of the mammalian transcriptome using DNA microarrays is now identifying hundreds of tissue-specific clock-controlled genes, which regulate an impressive diversity of biological processes.