Exactness and Approximation of the Stochastic Simulation Algorithm

This short note intends to clarify about the applicability of the Stochastic Simulation Algorithm proposed by Gillespie for the analysis of systems of coupled biochemical reactions. The derivation of Gillespie’s results is revisited to pinpoint those steps at which, depending on the validity of the assumptions adopted about the system to be studied, approximations may be introduced. We discuss about the ways the inaccuracies entailed by the approximations may propagate and affect simulation results.