The development and harmonious functioning of an organism depend on the exquisite coordination of myriad intertwined biological processes. As illustrated by this issue of Current Biology devoted to the ‘biology of time’, temporal organization plays crucial roles in coordinating dynamic phenomena as diverse as progression through the cell cycle, the processing of information, adaptation to the p...

We study the evolvability and dynamics of artificial genetic regulatory networks (GRNs), as active control systems, realizing simple models of biological clocks that have evolved to respond to periodic environmental stimuli of various kinds with appropriate periodic behaviors. GRN models may differ in the evolvability of expressive regulatory dynamics. A new class of artificial GRNs with an evo...

Recent experiments on the deamidation of glutaminyl and asparaginyl residues in peptides and proteins support the hypothesis that these residues may serve as molecular clocks that control biological processes. A hypothesis is now offered that suggests that these molecular clocks are set by rejection or accumulation of appropriate sequences of residues including a glutaminyl or asparaginyl resid...

Circadian (∼24 h) timekeeping is essential for the lives of many organisms. To understand the biochemical mechanisms of this timekeeping, we have developed a detailed mathematical model of the mammalian circadian clock. Our model can accurately predict diverse experimental data including the phenotypes of mutations or knockdown of clock genes as well as the time courses and relative expression ...

The circadian system in animals and humans, being near but not exactly 24-hours in cycle length, must be reset on a daily basis in order to remain in synchrony with external environmental time. This process of entrainment is achieved in most mammals through regular exposure to light and darkness. In this chapter, we review the results of studies conducted in our laboratory and others over the p...

A hierarchical system of clocks within cells throughout the body creates and synchronizes rhythmic functions from which life emerges. Biological circadian rhythms, linked to light and darkness in an organism’s environment, are generated by transcription-translation feedback mechanisms on universal “core” clock genes, e.g., Clock, Bmal1, Per1, Per2, Cry1 and Cry2 (16). Clocks within the brain br...