All Quiz 1 Answers - Question 1 a. (1 point) For each of...

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Question 1 a. (1 point) For each of the following properties, answer whether the statement is true for microtubules, actin, or both. i. it is involved in a cell moving around within a tissue (0.5 point) actin ii. it has a (+) end and a (-) end (0.5 point) both b. (2 points) You are interested in the regulation of the location of organelles within a cell, and decide to study the novel motor protein MOT1. In wildtype cells, the Golgi localizes immediately adjacent to the centrosome, which acts as the microtubule organizing center. In mot1- / mot1- cells, the Golgi is located farther away from the centrosome. What type of motor protein (dynein, kinesin, or myosin) is MOT1 most likely to encode, and why? (1 point) A dynein. (1 point) The centrosome is the location of the MTOC, so Golgi must be pulled towards the centrosome by a (-) end directed microtubule motor. c. (2 points) High resolution structural data allows you to determine that the distance between the two “heads” of MOT1 is 20 nm. You label one head of MOT1 with a fluorophore and perform single molecule measurements of MOT1 moving along the cytoskeleton. You get the following graph of MOT1 dynamics: Is the mechanism of MOT1 movement “inchworm” or “hand over hand”? Explain the reasoning for your answer. (1 point) inchworm (1 point) The step size is 20 nm, which is equal to the distance between the two heads.
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a. (1 point) For each of the following properties, answer whether the property is true for microtubules, actin, or both. i. it is used as a track for kinesins (0.5 point) microtubules ii. it is involved in muscle contraction (0.5 point) actin b. (2 points) You discover a novel protein, MAP10, that binds to the (+) end of microtubules. Additionally, you note that in map10 - / map10 - mutant cells, the microtubules are present near the spindle poles during metaphase but don’t reach the chromosomes in the middle of the cell. What is the probable wildtype function of MAP10, and what is a possible mechanism for this function? (1 point) MAP10 promotes the stability and/or growth of microtubules. (1 point) Since it binds to the (+) end of microtubules, one possible mechanism could be that MAP10 acts to prevent the hydrolysis of GTP to GDP of tubulin at the cap. Alternatively, it could act by preventing the bending of (+) ends of microtubules, since bending accelerates removal of tubulin subunits. c. (2 points) You next create an in vitro reconstituted system by adding purified centrosomes, tubulin, and MAP10 to cytosol extracted from frog eggs on a microscope slide. You are excited to see a difference in microtubule structures when wildtype MAP10 is added versus when mutant MAP10 is added. The wildtype structures are drawn for you. Draw the microtubule structures that forms when mutant MAP10 is added, and label the (+) and (-) ends. wildtype MAP10
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This note was uploaded on 01/28/2010 for the course MCB 104 taught by Professor Urnov during the Fall '09 term at University of California, Berkeley.

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All Quiz 1 Answers - Question 1 a. (1 point) For each of...

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