Before revision:  Despite many efforts to produce detailed mechanistic mathematical models of translation,  no basic and simple  kinetic model of mRNA lifecycle (transcription, translation and degradation) exists. We build such a model by lumping multiple states of translated mRNA into few dynamical variables and introducing a pool of translating ribosomes.
After revision:  Despite many efforts to produce detailed mechanistic mathematical models of translation, no basic and simple kinetic model of this process, derived directly from the detailed kinetic model. One of the reasons for this is that the translation process is characterized by indefinite number of states, thanks to existence of polysomes. We bypass this difficulty by applying a trick consisting in lumping multiple states of translated mRNA into few dynamical variables and introducing a pool of translating ribosomes.