CYBERNETIC CONSIDERATIONS. “Other regulatory units such as “plug-ins” (e.g. signaling pathways) and “on–off switches” linking subcircuits also perform an important role as flexible modular units. On the other hand, effector subcircuits perform cell biology functions such as cell shape changes or proliferation, while differentiation gene batteries comprise the terminal differentiation molecules necessary for the cell to perform its ultimate role in the organism.”
http://www.sciencedirect.com/science/article/pii/S0012160613004119