The relative occurrences of PIs in the predicted pathways and shuffled pathways. The relative occurrence of PIs are calculated from the predicted pathways based on our models and from the 100 simulations of shuffled pathways. The error bars are calculated by (2* standard error). The standard error is calculated from 100 simulations of shuffled pathways. Relative occurrences are calculated as (number of observed occurrences of PIs of type A~X)/(total number of observed occurrences of PIs of all types).