Overview

A growing cell culture is considered synchronous if cell divisions occur approximately simultaneously for all cells in other words, if the specific rate of cell division is not constant but alternates between low values, corresponding to an absence of cell divisions, and high values, corresponding to the synchronous cell divisions. Thus, in principle at least, any batch culture that is not in steady exponential growth or any continuous culture that is not in steady-state growth is partially synchronized.

The better the cell divisions are synchronized, the higher the "degree" or percent of synchrony is said to be. Although many attempts have been made to devise rigorous, quantitative measures of synchrony [12, 29, 30, 83, 104], the terms degree of synchrony, percent synchrony, and synchrony index are often used as self-explanatory, qualitative terms without any attempt to define them rigorously. Obviously, cell cycle synchrony reflects a deviation of the distribution of states from the shape it would have under steady growth conditions and a single number, such as degree of synchrony, is generally insufficient to fully characterize such a deviation. Furthermore, unless steps are taken to maintain synchrony, cell cycle synchrony is typically lost within a few generations and the degree of synchrony therefore decreases continuously.

Synchronous cultures are primarily used as a tool for study of the cell cycle and, at the current rate of scientific progress in cell biology, can only be considered ancient, with books devoted to the subject appearing as early as the 1960s [15,...