Properties of gene co-expression networks. (1A) Log-log plot of node degree and frequency distribution suggests that all microarray networks and their intersection - the Conserved network - are scale-free. (1B) Relationship between gene inclusion in the networks as a function of Pearson correlation coefficient (PCC). (1C) Relationship between the number of co-expression links (edges) as a function of PCC. (1D) Average network betweenness centrality as a function of PCC. (1E) Connected components as a function of PCC: at large PCC values, networks had a tendency to break down into a large number of connected components, i.e. unconnected subgraphs. (1F) Clustering coefficients as a function of PCC: as PCC threshold increased, genes within each subgraph lost the tendency to cluster together, a property reflected by the average clustering coefficient.