From 2007.igem.org

Genetic Schmitt Trigger - University of Bologna Cesena Campus 2007 Team. The aim of our project is to design, build and test a Genetic Schmitt Trigger. The Schmitt Trigger is a notable switch turned on at a threshold (Th) higher than the one responsible for the off transition (Tl), i.e. the stimulus activating the switch is higher than the one that shuts it off. The two distinct thresholds confer to the switch an improved noise margin via hysteresis which is usefully handled in control systems. Originally the Schmitt Trigger was realized as an electronic circuit, invented by Otto Schmitt who was inspired by its research on electric impulse propagation in squid axons. We are charmed by the idea to bring back this concept into biology. Indeed, hysteresis is already present in many biological systems, such as the lac Operon in E. coli: our goal is to build up a synthetic genetic device able to operate like a Schmitt Trigger.

We plan to assemble BioBricks from iGEM 2007 plates to make new ones mimicking some of the functional units of the lac operon labelled with a fluorescent tag to implement a (bio)synthetic sugar-driven switch which silences or activates the expression of a chosen gene.