Figure 1

Intrinsic and extrinsic noise as the source of the cell-to-cell variability in cellular responses in the NF-кB signaling networks. Intrinsic noise refers to the pure probabilistic nature of individual biochemical reactions in the signaling networks. Extrinsic noise refers to random interactions of the signaling networks with the external stochastic systems and originates from three sources: (i) fluctuating number of transcriptional regulators upstream of the signaling networks, (ii) fluctuating number of proteins inherited from parent cells, and (iii) different stages of their cell cycle.