Fig 2.

The mechanism of DNA looping could generate the phenomenon of “bistability.” The nonlinear response associated with the cooperativity of DNA looping, as well as a positive feedback in the regulation of the system, can generate bistability. Bistable systems can be in one state or another depending on their history, which can have consequences for the biology of the system. The pink area indicates the concentrations of inducer where the gene can be either repressed or expressed depending upon its initial condition (with low inducer or high inducer concentration).