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. Author manuscript; available in PMC: 2017 Dec 28.
Published in final edited form as: Phys Biol. 2008 Jun 16;5(2):026005. doi: 10.1088/1478-3975/5/2/026005

Figure 1.

Figure 1

(a) Schematic of a simple genetic network in which a protein activates its own transcription and (b) the phase portrait of the network dynamics. In mean-field theory, this network can exhibit bistable behavior with two stable fixed points (A and C), an intermediate unstable fixed point (B) and a separatrix (solid green curve) dividing the basins of attraction of the stable fixed points. Noise in transcription (gene → mRNA) and translation (mRNA → protein) can drive transitions between A and C. Inset: as discussed in the main text, switching is analogous to thermally-driven barrier crossing in a double well potential.