highly significantP = 1.58 10 −55
Gene Ontology enrichment analysis of the 155 genes in cluster 4 demonstrated a highly significant enrichment for biological processes linked with S phase including DNA replication ( P = 1.58 10 −55 ), DNA repair ( P = 1.31 10 −39 ) and G1/S transition ( P = 4.3 10 −26 ) (Fig. 1c , blue barplots).