Do Cells Cycle?

TLDR

After mitosis, cells enter an A‑state of non‑replicative activity that can last arbitrarily long, with a constant probability of exiting; exit leads to a deterministic B‑phase of replication, making initiation of cell division effectively random like radioactive decay. The study proposes that a cell’s life is divided into two fundamentally different parts. Cell population growth rates are determined by the probability of leaving the A‑state, the duration of the B‑phase, and the rate of cell death. Knowledge of these parameters permits precise calculation of the distribution of intermitotic times within populations, the behavior of synchronized cell cultures, and the shape of labeled mitosis curves.

Abstract

We propose that a cell's life is divided into two fundamentally different parts. Some time after mitosis all cells enter a state (A) in which their activity is not directed towards replication. A cell may remain in the A-state for any lenght of time, throughout which its probability of leaving A-state remains constant. On leaving A-state, cells enter B-phase in which their activities are deterministic, and directed towards replication. Initiation of cell replication processes is thus random, in the sense that radioactive decay is random. Cell population growth rates are determined by the probability with which cells leave the A-state, the duration of the B-phase, and the rate of cell death. Knowledge of these parameters permits precise calculation of the distribution of intermitotic times within populations, the behavior of synchronized cell cultures, and the shape of labeled mitosis curves.