Budding yeast models.

Nodes in the graph represent molecules, complexes, etc. Arrows with pointed heads represent activation, and arrows with bars indicate inhibition. Thin arrows represent a weight of 1/3, normal arrows represent a weight of 1 and thick arrows represent weight 3. (A) The model from Li, et al. [14]. (B) A subset of the model that highlights the first timing hazard. Nodes with values marked with * are enabled to change. If Cdc20 transitions from 1 to 0 before Cdh1 transitions from 0 to 1, Cdh1 will stay at 0, causing the cell cycle to arrest before it has returned to G1. (C) The hazard can be eliminated by replacing Cdc20 self-degradation with inhibition of Cdc20 by Cdh1, ensuring that Cdh1 transitions to 1 before Cdc20 transitions to 0. (D) The final speed-independent model for budding yeast.