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Unformatted text preview: BIS104 Winter 2010 Problem Set III “Due” Feb 22. This problem set will not be collected, but you should do it before looking at answers. Answers will be posted on Feb 22. 13. Below is a life history of the plus end of a single microtubule as recorded by video enhanced DIC microscopy. 1. What is the growth rate (polymerization rate) in ¡ m min1 ? 1 2. What is the growth rate in tubulin heterodimers per minute ? (An ¡¢ tubulin heterodimer is 8 nm in diameter.) 1625. 125 (which is 1 um devided by 8 nm) x 13 protofilaments 3. What is the catastrophe frequency? (units should be min1 ) 0.5. Remember that you can only have a catastrophe while growing. This MT was growing for 4 minutes and had 2 catastrophes. 4. What would the life history look like if you added each of the following reagents (in separate experiments)? Draw a graph of MT length over time. a. 10 μ M taxol Everything polymerizes b. 10 μ M colchicines No polymerization because tubulin subunits are sequestered c. MAP2 Increase in rescue frequency, longer microtubules d. XKCM1 Increase in catastrophe frequency, shorter microtubules 58. Below is a time course of actin assembly as monitored by light scattering. 5. What would happen if you added thymosin after 15 minutes?...
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 Spring '08
 Scholey
 Cell Cycle, Lucy Shapiro

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