Fig. 3.

Simulation of Mad2, BubR1, and Cdc20 mutations for each model variant.

For deletion we set the respective initial concentration to zero, and for over-expression 100 folds higher. Towards proper wild type functioning, APC:Cdc20 concentration should be very low (zero) before the attachment, and should increase quickly after attachment. Deletion of Mad2 or BubR1 or an overexpression of Cdc20 leads to inability of the cell to arrest, that is in the simulation, the concentration of APC:Cdc20 keeps high. Overexpression of Mad2 or BubR1 or deleting Cdc20 results in arresting the cell, that is, the concentration of APC:Cdc20 is very low or zero. Each row represents the mutation simulations of a model variant and a range of parameter rate for APC binding. Spindle attachment occurs at t = 2000 s (switching parameter u from 1 to 0). All parameter settings are according to Table 1. See text for more details.