BIS104 Starr W10 M2A Key PDF

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BIS 104 Form A

Midterm 2 March 5, 2010

Instructions: Be sure to mark the version of your test on the scantron. This is FORM A. There are 8 pages and 30 questions to this exam DO NOT OPEN UNTIL INSTRUCTED. The exam will end promptly at 9:50 am. If you think there is an error in the exam, notify the proctors. The proctors can’t help you define terms or clarify wording. Always pick the best answer. For each question there is one correct answer. Fill out your name and student identification number on the blue scantron Form with a #2 pencil. Fill in your answers on the scantron form with a #2 pencil. For each question only choose one answer (the best answer) and fill in your selection clearly and completely. If you change an answer, make you sure you erase it completely. There are 30 questions. 20 of them are worth 3 points, and 10 (indicated) are worth 4 points each for a total of 100 possible points.

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BIS 104 Form A

Midterm 2 March 5, 2010

Questions 1 through 3 are based on the below graph

C Light scattering

B

A 5 time (min)

10

15

1. Based on the actin filament assay presented in class, the concentration of monomeric G-actin at point C is __________ and actin subunits are _____________. A. greater than 0.8 M; adding at the barbed end and shrinking from the pointed end B. less than 0.8 M; adding at both ends C. between 0.8 M and 0.1 M; treadmilling D. greater than the critical concentration; adding at both ends E. less than the critical concentration; shrinking from the pointed end 2. Adding Thymosin protein to the A part of the graph, will prevent the ________ of actin filaments by ______. A. nucleation; sequestering G-actin B. growth; sequestering F-actin C. nucleation; blocking ARP2/3 D. shrinkage; prevent treadmilling E. growth; block growth at the + end 3. (4 points) At time point C (15 minutes) you do an experiment to add latrunculin, more monomeric actin, and ATP into the system and allow actin dynamics to proceed for 10 more minutes (to time point D; 25 minutes), at which time the actin filaments will once again be in steady state equilibrium. What would you predict to be the result of such an experiment? A. The concentration of F-actin at time D will be higher than at time C. B. The critical concentration at time D will be lower than at time C. C. The concentration of monomeric actin will be higher at time D than at time C. D. The amount of light scattering will be higher at time D than at time C. E. The concentration of F-actin remains constant.

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BIS 104 Form A

Midterm 2 March 5, 2010

4. The Starr lab studies two proteins (the SUN protein UNC-84 and the KASH protein UNC-83). UNC-84 localizes to the _____________ while UNC-83 localizes to the ___________. A. Nuclear pore complex; outer nuclear membrane B. outer nuclear membrane; inner nuclear membrane C. inner nuclear membrane; outer nuclear membrane D. nuclear lamina; inner nuclear membrane E. inner nuclear membrane; endoplasmic reticulum 5. KASH and SUN proteins UNC-83 and UNC-84 function to move nuclei through what mechanism? A. They recruit myosin to the surface of the nucleus to move it along actin filaments B. They recruit myosin to the surface of the nucleus to move it along intermediate filaments C. They recruit kinesin to the surface of the nucleus to move nuclei toward the minus ends of microtubules D. They recruit kinesin to the surface of the nucleus to move nuclei toward the plus ends of microtubules E. They recruit dynein to the surface of the nucleus to hold on to fluxing microtubules 6. Cyclin activation must occur in order throughout the cell cycle. Thus one role of a particular cyclin is to eventually activate the downstream cyclins. To keep the cell cycle in order, _________ stimulates the transcription of cyclin E and __________ stimulates the accumulation of cyclin B. A. Cyclin D; Cyclin E B. Cyclin B; Cyclin E C. Cyclin A; Cyclin D D. Cyclin D; Cyclin A E. Cyclin A; Cyclin F 7. Cyclin B/CDK1 has many targets. Which of the following is NOT a direct target for phosphorylation by active Cyclin B / CDK1? A. Securin B. Seperase C. cdh1 D. cdc20 E. wee1 8. If you wanted to target actin to the inside of the nucleus, what would you add to it? A. A lamin binding sequence B. A stretch of basic residues from the SV40 protein C. A ran-GTP binding domain D. Multiple ubiquination sites E. A KASH domain

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BIS 104 Form A

Midterm 2 March 5, 2010

9. 4 points) In order to understand anaphase onset more completely, you delete securin expecting premature sister chromatid separation. To your surprise, anaphase occurs at the proper time, not prematurely. You then do a screen for mutations that cause early sister chromatid separation in the securin deletion mutant background. You isolate a Serine to Alanine mutation in separase. You hypothesize that the point mutation in separase blocked __________, which normally prevents sister chromatid separation. A. Phosphorylation by cyclinB/CDK B. Ubiquitination by cdc20 C. Scc1 cleavage and opening of the cohesin ring D. Phosphorylation by wee1 E. Phosphorlyation by cdc25 10. (4 points) What happens to children who inherit a loss-of-function mutation in Rb? A. E2F is repressed B. Cyclin D levels are elevated C. Cyclin E levels are elevated D. Cells re-enter S phase from G2 E. Cells arrest in G1 11. (4 points) Taxol is used as an anti-cancer agent. Its mechanism is to ___________ microtubules and to kill cancer cells by _______________. A. stabilize; arresting cells in mitosis B. increase the turnover of; ignoring the spindle assembly checkpoint C. depolymerize; blocking mitosis D. decrease the turnover of; allowing them to by-pass the spindles assembly checkpoint E. decrease the turnover of; inducing p53 12. You isolate a mutation in which Ran is stuck in a GTP-bound form. In such a cell you notice that a GFP with a nuclear localization signal (NLS) that normally is targeted to the nucleus is now in the cytoplasm. Why? A. The NLS-GFP can no longer bind Ran B. The nuclear pore complex is closed C. -importin is sequestered by Ran D. -importin is stuck in the nucleus E. RCC1 is not active 13. (4 points) In inactivated platelets flowing through the blood, the concentration of Gactin is kept ________________. A. low by decreasing the critical concentration B. high by translating more G-actin C. high by decreasing the critical concentration D. high by sequestering with profilin E. high by CapZ

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BIS 104 Form A

Midterm 2 March 5, 2010

14. If you microinjected a cell with cyclinB 90 protein (deletion of the first 90 amino acids of cyclin) during metaphase, what would happen to the distance between the centrosome and the chromosome after waiting for 1 hour? A. Grow B. Shrink C. No change D. Impossible to predict 15. A variety of important model organisms have elucidated different aspects of the cell cycle. The molecular nature of cyclin-dependent kinases and the fact that they are required at multiple steps in the cell cycle was discovered using ______________. A. Genetics in the fission yeast S. pombe B. Biochemistry in Sea Urchin embryos C. Biochemistry in Xenopus oocytes D. Biochemistry in mammalian tissue culture cells E. Genetics in Xenopus oocytes 16. (4 points) Energy is required to import proteins into the nucleus. Which of the reasons below is the main energy consumer of nuclear import. A. Setting up the proton gradient across the nuclear membrane using an ATPase B. Using a microtubule motor to move a protein through the nuclear pore complex C. Each time a protein is imported into the nucleus, importin is ubiquinated and degraded D. Opening and closing the gated nuclear pore complex E. Setting up the Ran GTP gradient 17. The cytoskeleton plays many important roles in the cell including the localization of many organelles in the cell. The ER localizes along the length of _________. The motor responsible for localization there is _________ . A. actin filaments; Myosin V B. microtubules; Dynein C. intermediate filaments; Dynein D. microtubules; Kinesin E. actin filaments; Myosin II 18. (4 points) cdc25, which is required for anaphase, is highly regulated throughout the cell cycle. ______activates cdc25, while _____ inhibits cdc25. A. cyclin/CDK; cdc20 B. Ubiquitin ligase; cyclin/CDK C. wee1; mad2 D. MPF; chk1 E. cdc2; p53

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BIS 104 Form A

Midterm 2 March 5, 2010

19. MDM2 normally directly inhibits p53 activity by destabilizing p53. You would therefore predict that MDM2 has which of the following properties? A. MDM2 is a proto-oncogene B. MDM2 is a tumor suppressor gene C. MDM2 activity increase apoptosis D. MDM2 activity slows down the cell cycle E. MDM2 would be shuttled out of the nucleus by Ran GDP 20. Nucleation of both actin filaments and microtubules is the rate-limiting step of in vitro assays of filament polymerization. You learned in class that ________ directly nucleates actin filaments, while ________ nucleates microtubules in mammalian cells. A. ActA; -tubulin B. Centrosomes; leading edge C. ARP2/3; -TuRC complex D. WASP; centrioles E. WASP; ARP2/3 21. Plants, animals and bacteria (at least Caulobacter) perform cytokinesis in different ways. Which of the following statements is true? A. All three have a contractile ring, in animals its actin/myosin, plants its microtubules/kinesin, and in Caulobacter its made of a tubulin homolog. B. The actin homolog in Caulobacter (MreB) functions just like actin in animal cells to pinch apart daughter cells. C. Caulobacter are like plant cells, they traffic vesicles to the midzone and build a new cell wall between the daughter cells. D. Caulobacter use FtsZ to pinch apart the daughter cells. E. The video didn’t discuss how Caulobacter undergo cytokinesis, it focused on how it segregated DNA. 22. You return from an expedition to the Amazon with a suitcase of compounds from rare plants. When you inject these compounds into cells, endocytosis of clathrin-coated vesicles is blocked. You determine that the compound blocks the ATPase activity of a motor. You hypothesize that this compound disrupts the activity of the motor_________. A. Myosin II B. Myosin V C. Dynein D. Kinesin E. Myosin VI 23. Which of the following is a role of the active cyclinE/CDK2 complex? A. To target cdc6 for degradation to allow entry into S phase B. To activate Rb, which releases E2F to initiate S phase C. To inhibit DNA polymerase and prevent the re-initiation of S phase D. To inhibit wee1 so the cell can pass the START point E. To induce cdc20 to target the degradation of cyclin E and exit from mitosis

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BIS 104 Form A

Midterm 2 March 5, 2010

24. (4 points) In class we discussed the initial discovery of the first dynein and first kinesin. Dynein was originally discovered by __________ and kinesin by ___________. A. removing dynein from cilia with EDTA (which chelates Mg2+ ions); blocking in a rigor state with non-hydrolizeable ATP. B. purifying dynein from giant squid axons; blocking kinesin in a rigor state by removing all ATP C. homogenizing cilia to break off dynein; by cloning unc-104 that disrupts C. elegans axons D. purifying dynein from kinetochores in Drosophila embryos; biochemical purification of kinesin from giant squid axon extracts E. purifying dynein from COPI vesicles; purifying kinesin from Drosophila embryos 25. Microtubules (MT), microfilaments (MF), and intermediate filaments (IF) are all dynamic structures. Which of the following statements best describes how these three filaments are dynamic. A. MT dynamic instability; MF treadmill; IF exchange subunits from the middle B. MT treadmill; MF dynamic instability; IF treadmill C. MT dynamic instability; MF exchange subunits from the middle; IF treadmill D. MT treadmill; MF dynamic instability; IF exchange subunits from the middle E. MT dynamic instability; MF and IF exchange subunits from the middle 26. (4 points) cdc20 plays a central role in progression through the cell cycle. Different proteins have different effects on cdc20. Which of the following statements best describes cdc20? A. cdc20 is a kinase that is inhibited by the chk1 kinase and stimulated by CDK. B. cdc20 is an ubiquitin ligase that is activated by MPF and inhibited by Mad2. C. cdc20 is an ubiquitin ligasethat is phosphorylated by cdc25 and inhibited by DNA damage. D. cdc20 is a phosphatase that removes the phosphate on Thr 161 of CDK that was placed there by wee1 kinase. E. cdc20 is a phosphatase that is inhibited by DNA damage and activated by CDK 27. (4 points) You isolate a temperature sensitive mutation in a chromokinesin in Drosophila. At the restrictive temperature, the cell arrests in mitosis. Why? A. The kinetochore can not attach to microtubules B. The kinetochore induce catastrophes at the + end of microtubules C. The astral repulsion force is missing D. Interpolar microtubules can not slide apart E. Poleward flux is turned off 28. When the spindle assembly checkpoint is activated, which of the following occurs? A. All sister chromatids are under bi-polar tension B. Separase is active C. Mad2 sequesters cyclin B D. Securin is stabilized E. Cdc20 activity is high

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BIS 104 Form A

Midterm 2 March 5, 2010

29. You look at a population of microtubules in a cell using an electron microscope. Some of the microtubules have curved protofilaments at the end. You hypothesize that such a microtubule was ______________ at the time of fixation. A. Growing by adding on GTP-bound tubulin B. Growing by adding on GDP-bound tubulin C. Had just had a rescue event D. Shrinking with a GTP-tubulin cap E. Shrinking with a GDP-tubulin cap 30. Dynein is used for many different things in the cell. Which of the following is NOT a role for dynein? A. Movement of flagellum B. Movement of kinetochores in prometaphase towards the centrosome C. Keeping the spindle poles apart in mitosis D. Transport of neurotransmitters down the axon towards the synapse E. Vesicle trafficking from the ER to the Golgi

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