Oscillations in Biology

Experiments in molecular biology are generally performed in a static state; analytes are frozen in time and displayed as if there had been no changes over time. Yet, biology is dynamic, responding to internal regulatory demands, external stimuli and evolutionary pressures. There are fundamental rhythms in biological systems such as ovulation in humans and estrus in animals. At the cell level, day-night synchronization, the 24 h circadian cycle created by a feedback loop of gene circuits, affects vital functions. Disruption of the circadian cycle has been shown to have protean health consequences. In contrast, little is studied about the rhythms independent of 24 h clock. This article reviews the non-circadian rhythms in biological systems existing at the transcriptional level; inherent problems and biases in detecting these from biological data and the use of mathematical methods in overcoming these biases.