The continuum model and G1-control of the mammalian cell cycle.

The continuum model of the mammalian division cycle proposes that there are no G1-phase specific controls or events. The G1 phase is simply the time when processes begun in the previous cell cycle are completed. In this review, the continuum model is applied the variability of the G1-phase, the existence of G1-less cells, the ubiquitous G1-phase arrest phenomenon, the effect of over-expressed cyclins on G1-phase length, the statistical variation of the cell cycle, the reports of G1-phase syntheses, the proposed variation in retinoblastoma protein phosphorylation in G1-phase, and the myriad findings put forward to support the G1-control model of the mammalian division cycle. The continuum model is a valid description of the mammalian division cycle.