Occurrence of cell division is not exponentially distributed: differences in the generation times of sister cells can be derived from the theory of survival of populations.

The Eyring-Stover survival theory has been applied to the kinetics of the distribution of intermitotic intervals of mammalian cells and by inference to the transition from the G1 phase into DNA synthesis (S phase). The theory faithfully fits experimental data acquired by time-lapse cinemicrography of cloned HeLa cells in tissue culture and also suggests the existence of a labile initiator substance which mediates the G1-S phase transition. This theory provides an alternative to the transition probability model proposed by Smith and Martin [Smith J. A. & Martin, L. (1973) Proc. Natl. Acad. Sci. USA 70, 1263-1267; see also Shields, R. & Smith, J. A. (1977) J. Cell Physiol. 91, 345-355 and Brooks, R. F., Bennett, D. C. & Smith, J. A. (1980) Cell 19, 493-504].