Sizing Up the Cell

The coordination of cell growth and division is responsible for fundamental characteristics of cells such as their size: Fast growth with slow division makes big cells, whereas slow growth with fast division makes small cells. Yet despite decades of effort, the kinetics of cell growth and its influence on cell division have remained elusive topics, at least for animal cells. Is cell growth linear (constant) or exponential (proportional to cell size)? Does cell division occur after cells have grown beyond a minimum size, or is there rather some “age of consent” for division, or both? A report by Tzur et al. on page 167 of this issue ( 1 ) combines a new experimental method with careful mathematical analysis to answer these questions for cultured mammalian lymphoblasts.