Fig. 1
Schematic representations of the one- and two-state models. In the one-state model (top), mRNA is produced at a constant rate (k 1). Protein is produced from mRNA with first order kinetics at a rate k 2. Both mRNA and protein molecules are degraded according to first order kinetics with rates d 1 and d 2 respectively. The two-state model (bottom) has the added feature of two promoter states. In the inactive state the promoter produces mRNA at a fraction (k 0) of that of the active state. Switching between the two states corresponds to a telegraph process characterised by two rate constants (k on and k off)