Further extensions and concluding remarks

The mitotic oscillator a role for positive and negative feedback 

The onset of mitosis in eukaryotic cells is controlled by a phosphorylation-dephosphorylation cascade behaving as a continuous biochemical oscillator. The outcome of the cascade is the periodic activation of cdc2 

Time delays also play a significant role in the onset of oscillations in the cascade. Such time delays result here in a natural way from the thresholds in the activation curves of cdc2 kinase and cyclin protease, and are by no means inserted in an ad hoc manner into the kinetic equations (10.1), as is often done for systems governed by time-delay differential equations. 

Although the cascade model shows that the mitotic oscillator might 

The somatic cell cycle as a double, cdc2-cdk2 oscillator The cell cycle in yeast and in somatic cells appears to be more complex than in embryonic cells as it is subjected to additional controls linking, for example, the onset of mitosis to the successful completion of DNA replication or to the reaching of a critical cellular size (Cross et al, 1989  

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