Transitions of an arbitrary polymer . To relate the final chain to the growing chain, it is useful to consider fluxes through interfaces in this transition diagram. Using the tip and combined probabilities, along with relative propensities, it is possible to describe the fluxes through interfaces 4 to 7 in terms of properties of the growing chain. Equally, by considering errors and conditional errors and taking fractions of the overall growth velocity, it is possible to find the fluxes through interfaces 4 to 7 in terms of properties of the final chain and growth velocity.