Kirschner, Marc

Kirschner, Marc W., and John C. Gerhart. The Plausibility of Life Resolving Darwm s Dilemma. New Haven, Conn. Yale University Press, 2005. 

The GDP-tubulin subunits in the interior length of a microtubule remain stably polymerized, whereas GDP subunits exposed at an end have a strong tendency to dissociate. Marc Kirschner and Tim Mitchison found that some microtubules in a population lengthen while others simultaneously shorten. This property, called dynamic instability, arises from random fluctuations in the number of GTP- or GDP-tubulin subunits at the plus end of the polymer. The dynamic character of microtubules is crucial for processes such as mitosis, which require the assembly and disassembly of elaborate microtubule-based structures. 

Murray, Andrew W., and Marc W. Kirschner. "What Controls the Cell Cycle. Scientific American (March 1991). 

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