Model-generated best fits. Blue lines represent model simulation; red diamonds represent in vivo data points. PEL indicates a chromatin-bound species (pellet); SUP indicates non-chromatin bound (supernatant); NUC indicates nuclear fraction. The error bars indicate the variance calculated from triplicate experiments. Since the Cdt1 and Dbf4 data  and , respectively was not reported with variance values, we assigned values to these factors equal to the variance from the corresponding time-point for Cdc45, as these have similar abundances compared to other proteins in the model. The observed quantities correspond to the model state variables as follows: CDC6PEL = RC2 + RC3, CDC6SUP = CDC6N, CDC45PEL = RC6 + FORK, CDC45SUP = CDC45N, DBF4PEL = RC5 + RC6, DBF4SUP = DBF4N, MCMPEL = RC3 + RC4 + RC5 + RC6 + FORK, MCMSUP = MCMN + MCM·CDT1N + MCMC, and CDT1NUC = CDT1N + MCM·CDT1N. One MCM molecule represents two MCM hexamers. Similarly one molecule of Cdc45 represents two individual such proteins.