We present an analytical treatment of a genetic switch model consisting of two mutually inhibiting genes operating without cooperative binding of the corresponding transcription factors. Previous studies have numerically shown that these systems can exhibit bimodal dynamics without possessing two stable fixed points in the deterministic rate equations . We analytically show that bimodality is induced by the noise and reveal the critical repression strength which controls a transition between the bimodal and non-bimodal regimes. Moreover, we show that the mean switching time between bimodal states scales polynomially in the system size . These results, independent of the model under study, reveal essential differences between these systems and systems with cooperative binding  .
We present an analytical treatment of a genetic switch model consisting of two mutually inhibiting genes operating without cooperative binding of the corresponding transcription factors. Previous studies have numerically shown that these systems can exhibit bimodal dynamics without possessing two stable fixed points at the deterministic level . We analytically show that bimodality is induced by the noise and find the critical repression strength that controls a transition between the bimodal and non-bimodal regimes. We also identify characteristic polynomial scaling laws of the mean switching time between bimodal states . These results, independent of the model under study, reveal essential differences between these systems and systems with cooperative binding , where there is no critical threshold for bimodality and the mean switching time scales exponentially with the system size .
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in the deterministic rate equations
at the deterministic level
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reveal
find
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which
that
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Moreover, we show that
We also identify characteristic polynomial scaling laws of
D
scales polynomially in the system size
A
, where there is no critical threshold for bimodality and the mean switching time scales exponentially with the system size