Midterm1.130.05 - MCB130 Midterm 1 Fall `05 Signature SID Name GSI Use only the space provided below to answer each question Do not write on the

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Unformatted text preview: MCB130, Midterm 1 Fall `05 Signature: SID: Name: GSI: Use only the space provided below to answer each question. Do not write on the back. For maximal credit, leave out extraneous information. 100 points total. 1. (10pts) How are sister chromatids held together in mitosis and how are chromosome homologs held together during meiosis I? 2. (12 pts) Provide three reasons why intermediate filaments can not exhibit treadmilling. 3. (16 pts) Briefly describe the function of each of the following skeletal muscle proteins. (a) The troponin complex (b) Tropomodulin (c) Nebulin (d) Titan 1 MCB130, Midterm 1 Fall `05 Signature: SID: Name: GSI: 4. (15 pts) Motivated by the efficacy of taxol as a chemo-therapeutic agent for certain cancers, a biotechnology company decides to develop candidate drugs against non-tubulin microtubule-associated targets. Predict how a chemical inhibitor of each of the following targets might affect mitosis. Explain your answers. Refer to specific events in mitosis. (a) Human homologue of BimC (b) Kin I kinesin (e.g., XKCM, MCAK) (c) Stathmin/Op18 5. A researcher allows a solution of tubulin monomers to assemble to steady state in the presence of GTP. (a) (4 pts) What is the term used to describe the monomer concentration at steady state? (b) (8 pts) The researcher allows a reaction of pure tubulin plus GTP to reach steady state. He then dilutes the reaction 2-fold (with the same GTP-containing buffer in which he carried out the assembly), and quickly views the microtubules by DIC microscopy. To his surprise, while most of the microtubules are disassembling, he finds a few that continue to assemble. Provide an explanation for the existence of this assembling population of microtubules. 2 MCB130, Midterm 1 Fall `05 Signature: SID: Name: GSI: 6. (20 pts) Lamellipodium protrusion plays an important role in cell motility and involves the active assembly of actin filaments at the leading edge. Briefly describe the significance of each of the following in the context of cell motility. (a) WASP (b) capping protein (c) ADF/cofilin (d) profilin (e) filament bundling/crosslinking 3 MCB130, Midterm 1 Fall `05 Signature: SID: Name: GSI: 7. (15 pts) Solutions of F-actin can be very viscous*. If two solutions contain the same amount of F-actin, but in one case the filaments are shorter than in the other case, the solution with shorter filaments will be less viscous. A student identifies a new actin-binding protein and names it drubinin in honor of his MCB 130 professor. He assembles the same amount of actin in the presence or absence of the protein and measures the extent of assembly, rate of assembly, and viscosity of the final solution of assembled actin filaments. He finds that drubinin does not affect the final extent of assembly, but that the viscosity of actin assembled in the presence of the protein is reduced compared to that in the reaction without the protein. The kinetics of the two assembly reactions are shown below (both in the presence of ATP). Actin plus drubinin assembly Pure actin time * Viscosity is defined as resistance of a solution to flow. Present a hypothesis for the biochemical activity of this protein. Provide an explanation for the effects of drubinin on assembly kinetics and viscosity. 4 ...
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This note was uploaded on 04/02/2008 for the course MCB 130 taught by Professor Schekman during the Spring '08 term at University of California, Berkeley.

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