Table 1.

Variables of the model.

symbol	definition
Mda	cyclin D/Cdk4–6 complex
E2F	transcription factor E2F
Me	cyclin E/Cdk2 complex
Ma	cyclin A/Cdk2 complex
Mb	cyclin B/Cdk1 complex
Cdc20	protein that belongs to the anaphase-promoting complex (APC)

^aMd is uncoupled from the other variables and rapidly reaches a steady state. The model thus contains only five variables.