We consider a bistable genetic switch consisting of two operons. For each, the regulatory region produces a repressor molecule that is inactive unless it is combined with the effector produced by the opposing operon. In the combined form the repressor-effector complex binds to the operator region and  blocks transcription of the corresponding structural gene. When the  operator region is not complexed with the active form of the repressor, transcription of the structural gene can take place and mRNA  is produced. Translation of the mRNA then produces an  effector molecule. These effector molecules then are capable of interacting with the repressor molecule of the opposing gene. We study limiting dynamics of bistable  switches with and without noise.

(joint work with Michael C. Mackey)