Genetic clock of biologic rhythms.

Biologic rhythms are tightly regulated in all species, in order to adapt to circadian variations of light, temperature and other biological related living conditions. The intrinsic mechanisms of rhythm regulation from every cell to a whole organism is embedded into the genetic clockwork. The mammalian clock genes are reviewed with their interrelation. The per gene promoter is stimulated by clock/bmal1 heterodimer and trigger the per proteins synthesis. Initially considered as a simple negative feed-back, from to the phosphorylated per/cry heterodimer towards clock/bmal1 transcription stimulus, the clockweb of the cell became complex. General characteristics of cell clock genes are integrated in a model. In addition, the involvement of clock genes in peripheral tissues is discussed.