It has been previously suggested that both the coding and the associated non-coding sequences of some human-mouse orthologs could evolve as a single unit. This letter deals with the observation that between mouse and humans some orthologs change significantly their compositional features as an indication that the molecular evolution is a local process. Moreover, the data shown indicate that the coding and the intron sequences of these orthologs do not evolve independently but instead both undergo a concerted evolution, evolving as a single unit, from a compositional cluster in mouse to a different compositional cluster in human.
Keywords: Co-evolution; Gene clustering; Molecular evolution; Triplet composon.