Two-Subcycle Cell Cycle Model

The two-subcycle cell cycle model has been developed from a mouse embryonal carcinoma cell line system (F9, PCC3 N/1, and PCC4 Azal). The slopes of the curves were calculated and put into the equation representing the two-subcycle cell cycle model. The concept of random transition was introduced in the early 1970s to describe cell cycle progression. It was based on the appearance of negative exponential distribution of cell population interdivision time (IDT) values (alpha curve) and distribution of IDT differences between sister cell pairs (beta curves) when plotted in semilogarithmic graphs. Since cell volume was estimated for spherical mitotic and postmitotic cells in a growing cell population, there was no direct observation of alterations of growth rate during interphase. Since cycling cells can drop out of the cell cycle and remain quiescent for a long time but still have the capacity to enter the cell cycle again a cell state, denoted GO, was proposed for them.