Before revision: We present a stochastic framework to study signal transmission in a generic two-step cascade S \rightarrow X \rightarrow Y. Starting from a set of Langevin equations obeying Gaussian noise processes we calculate the variance and covariance associated with the system components .
After revision: We present a stochastic framework to study signal transmission in a generic two-step cascade S \rightarrow X \rightarrow Y. Starting from a set of Langevin equations obeying Gaussian noise processes we calculate the variance and covariance while considering both linear and nonlinear production terms for different biochemical species of the cascade .