Dynamics of the cell cycle: checkpoints, sizers, and timers
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Updated: Aug 30, 2026

Temporal Tracking of Cell Cycle Progression Using Flow Cytometry without the Need for Synchronization
Published on: August 16, 2015
Zhilin Qu1, W Robb MacLellan, James N Weiss
1Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at University of California, Los Angeles, California 90095, USA. zqu@mednet.ucla.edu
Abstract:
We have developed a generic mathematical model of a cell cycle signaling network in higher eukaryotes that can be used to simulate both the G1/S and G2/M transitions. In our model, the positive feedback facilitated by CDC25 and wee1 causes bistability in cyclin-dependent kinase activity, whereas the negative feedback facilitated by SKP2 or anaphase-promoting-complex turns this bistable behavior into limit cycle behavior. The cell cycle checkpoint is a Hopf bifurcation point. These behaviors are coordinated by growth and division to maintain normal cell cycle and size homeostasis. This model successfully reproduces sizer, timer, and the restriction point features of the eukaryotic cell cycle, in addition to other experimental findings.
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