User:Jtwsaddress42/Projects/Project 2/Sections/Chapter 2/Animal Cells - Divide Or Differentiate, But Not Both At The Same Time

Animal cells only have one microtubule organizing center (MTOC) per cell, and a choice in how it can be used at any given time. The MTOC can either nucleate microtubules to be used to differentiate the cytoskeletal architecture; or, the MTOC can be used to form the meiotic and mitotic spindles that participate in the separation of the chromosomes during cell division. In order for an animal cell to divide, it must retract its cytoskeleton and become ameoboid, so that it can redirect its MTOC to the process of division instead. This restriction has interesting consequences for animal evolution as a multicellular organism.

The cytoskeleton is comprised of a variety of microfilaments, intermediate filaments and microtubules - all of which can undergo dynamic assembly and/or disassembly to control fiber length during morphological transformations of the cells overall shape. It is the mutual requirement of the microtubules in cytoskeletal differentiation and cellular replication that sets the constraints on animal body plan organization. It appears that this very constraint may have been the necessary requirement to direct the bifurcation of the early animal bodyplan into germ and soma.