Unformatted text preview: Student number__________ Grader number___________ Biol110-Cell Biology Fall 2010 Problem Key #7 Question #2- The Cytoskeleton, Its Motors and Muscle Contraction What does the term ‘dynamic instability’ stand for? Explain. Why is dynamic instability enhanced at the onset of mitosis? (5 pts) Dynamic instability describes the polymer dynamics of microtubule filaments inside cells (1 pt) as: they constantly elongate and shrink (1 pt) depending on the concentration of monomers (for polymerization) and random catastrophes (for depolymerization) (1 pt). Dynamic instability keeps the microtubule cytoskeleton poised to change shape or re-locate at any time in response to extracellular or intracellular cues (1 pt), as in preparation for mitosis when the tubulin subunits in centrosomes need to rearrange into spindles (1 pt) Why do cells actively nucleate actin and microtubule filaments rather than relying on spontaneous polymer initiation? Where and how is microtubule and actin filament nucleation accomplished at a polymer initiation?...
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- Fall '10