We discuss a model for transport properties in a donor-acceptor system connected by a dimerized chain. The system is assumed to be subject to site-diagonal disorder. The average spectral properties of the system are discussed by using the random matrix Wegner model (Anderson＇s type tight-binding Hamiltonian (TBH)) for the electronic part of the problem. In our analysis we use the "Blue＇s function" (functional inverse of the resolvent) formalism. For a simple one-dimensional tight-binding picture, we show that the diagonal disorder destroys the energy gap emerging as a Peierls effect in a nonperturbed system without disorder, rederiving thus the results obtained earlier using different models of site randomness.