Time allowed: 2 hours Answer ALL questions in Section A, ALL PARTS of the question in Section B and ONE question from Section C.

Transcription

1 UNIVERSITY OF EAST ANGLIA School of Biological Sciences Main Series UG Examination CELL BIOLOGY BIO-2B06 Time allowed: 2 hours Answer ALL questions in Section A, ALL PARTS of the question in Section B and ONE question from Section C. Write answers to EACH SECTION in the Answer Grid or SEPARATE booklet. The maximum number of marks available for your answers in SECTION A is 40 marks The maximum number of marks available for your answer in SECTION B is 30 marks The maximum number of marks available for your answer in SECTION C is 30 marks The TOTAL number of marks available for the paper is 100 Numbers in square brackets [ ] indicate the relevant mark applied to each part of the question. Notes are not permitted in this examination. Do not turn over until you are told to do so by the Invigilator. BIO-2B06 Module Contact: Dr Jelena Gavrilovic, BIO Copyright of the University of East Anglia Version 1

2 2 SECTION A: MULTIPLE CHOICE AND SHORT ANSWER QUESTIONS Answer ALL questions. Answer multiple choice questions in the answer grid provided and attach this to your booklet for Section A. 1. Collagens are composed of which of the following: a) two polypeptide chains b) three polypeptide chains c) three DNA polymers d) two DNA polymers e) four polypeptide chains 2. An early event following cell attachment to an ECM component via most integrins is: a) the intracellular domain of the integrin undergoes autophosphorylation b) FAK is recruited and undergoes autophosphorylation c) the intracellular domain of integrins is de-phosphorylated d) the ECM component is phosphorylated e) the integrins are internalised with the ECM component 3. LAD-I (Leukocyte Adhesion deficiency-i) results from a defect in the synthesis of: a) Beta-2 integrins b) Alpha-1 integrins c) TGF-alpha d) TGF-beta e) TNF-alpha 4. Which of the following is characteristic of both mitosis and meiosis? a) Chromosomes attach to spindle fibres composed of actin. b) The resulting cells are all diploid (2n). c) The resulting cells are all haploid (1n). d) Spindle fibres attach to chromosomes at their kinetochores. e) Both involve a single round of cell division. Section A continues on next page/...

3 3 Section A continued HAT (hypoxanthine-aminopterin-thymidine) medium is used to: a) immortalize B-lymphocytes. b) fuse B-lymphocytes to myeloma cells. c) select for hybrids in the hybridoma technique. d) kill B-cell hybridomas. e) prevent antibody production. 6. In the Ras and MAP kinase pathway, the last step in the pathway is catalyzed by MAP-kinase. Once activated, the main function for MAP-kinase is to: (a) bind to Grb2 (b) phosphorylate a transcription factor (c) activate adenylate cyclase (d) activate phospholipase C (e) bind to glucocorticoid response elements 7. Which of the following tissues has very limited capacity to self-renew? a) Brain b) Gut c) Bone d) Liver e) Skin 8. A pre-requisite for regeneration of peripheral nerves is the process of: a) Lieberkuhnian degeneration b) Smithsonian degeneration c) Wallerian degeneration d) Etonian degeneration e) Hypotonian degeneration 9. In the haemopoietic cell lineage, dendritic cells are produced by: [1mark] a) lymphoid progenitor cells b) myeloid progenitor cells c) muscle progenitor cells d) erythroid progenitor cells e) natural killer cells Section A continues on next page/... TURN OVER

4 4 Section A continued Which of the following statement(s) on mammalian initiator caspases is correct? a) Initiator caspases are expressed as inactive pro-enzymes b) Initiator caspases contain an essential histidine residue in the active centre c) Initiator caspases are found concentrated on the membrane of the endoplasmic reticulum d) Initiator caspases cleave nuclear proteins (nuclear lamins; transcription factors) e) Caspase-3 is a typical initiator caspase 11. Ca ++ ions play an important role during the process of apoptosis. Which of the following statements on the function of Ca ++ is incorrect? a) Ca ++ can activate signalling pathways, like protein kinase C (PKC) signalling b) Ca ++ ions are present at high concentration only in the cytosol c) Crosslinking transglutaminase enzymes can be activated by Ca ++ d) Changes in the cytoskeleton may be induced by increased Ca ++ concentrations e) Distribution of some lipids in plasma membranes is influenced by Ca ++ levels 12. TUNEL analysis (TdT-mediated dutp Nick End Labeling) can be used in the analysis of apoptosis and specifically detects: a) degradation of nuclear lamins b) fragments of mrna c) changes in membrane polarity d) cytoskeletal alterations e) increased amounts of DNA ends 13. Which of the following is an actin filament nucleator? a) Gamma-tubulin b) Plectin c) Arp2/3 d) Kinesin a. Cofilin Section A continues on next page/...

5 5 Section A continued Which intermediate filament type is highly expressed in epithelial cells? a) Cadherin b) Desmin c) Neurofilaments d) Lamin B e) Keratin 15. Which of the following is nucleated at the centrosome? a) Actin b) Myosin c) Microtubules d) Intermediate filaments e) Neurofilaments 16. Different parts of the developing embryo are formed by the process of: a) preformation b) gastrulation c) epigenesis d) evolution e) ontogeny 17. Which one of the following is derived from the endoderm? a) Heart b) Muscle c) Liver d) Blood e) Bone 18. The dorsal-ventral axis of an embryo corresponds to its: a) head and tail b) front and back c) left and right d) up and down e) inside and outside Section A continues on next page/... TURN OVER

6 6 Section A continued Regulation of gene activity is important for: a) pattern formation b) cell differentiation c) morphogeneis d) growth e) all of the above For all remaining questions in Section A, please use an answer booklet. Remember to attach your multiple choice answer grid to the booklet. 20. Show with a simple diagram the three main categories of growth in vertebrates. [3 marks] 21. Somites give rise to a number of different tissues in the body. Where are they found in the embryo and what tissues do they give rise to? [4 marks] 22. You have cloned the cdna for a novel putative signal-dependent mammalian transcription factor (factor A) and determined in vitro that it binds to a specific DNA sequence which you have named an ARE, for factor A-responsive element. Briefly describe an experiment that you could perform to determine whether factor A can activate transcription via binding to the ARE, in response to the signaling molecule GF1, in whole cells. [5 marks] 23. State three defining features of the innate immune system. [3 marks] 24. Match the following integrin pair with its most common ECM ligand. [3 marks] (i) Alpha 5 beta 1 integrin (ii) Alpha 1 beta 1 integrin (iii) Alpha 6 beta 1 integrin (a) Laminin (b) Type I Collagen (c) Fibronectin 25. Briefly state three important functions of hepatocytes. [3 marks] END OF SECTION A START YOUR ANSWER TO THE NEXT SECTION IN A NEW BOOKLET Section B begins on next page/

7 7 SECTION B: DATA HANDLING QUESTION Answer ALL PARTS of the question [30 marks] 26. A new microtubule associated protein (MAPX) has been discovered and its influence on microtubule stability and dynamics was investigated in cells expressing low (cell type A) and high (cell type B) levels of MAPX. Microtubule stability was first investigated by determining the expression level of detyrosinated tubulin by western blotting. The presence of detyrosinated tubulin is an indicator of stable microtubules. Cell extracts were prepared from both type A and B cells and western blots were probed for detyrosinated tubulin and -tubulin and the results are shown in Figure 1 below. Detyrosinated tubulin Cell type A Cell type B α-tubulin Figure 1. Western blot showing expression levels of detyrosinated tubulin in cell extracts from cell types A and B. The expression level for -tubulin was used as a loading control. (a) What do the western blot results suggest about the effect of MAPX on microtubule stability? [5 marks] Next, both cell types A and B were incubated at 4 C for 30 minutes, immune-labelled for microtubules and imaged in a fluorescence microscope. Analyses revealed that almost all type A cells had no microtubules whereas type B cells contained a significant number of microtubules. (b) Explain these observations bearing in mind the effect of cold on microtubules. [5 marks] (c) Explain whether the findings from the cold treatment experiment support the Western blot results? [2 marks] Section B Q26 continues on next page/... TURN OVER

8 % microtubules 8 Section B Q26 continued The effect of MAPX on microtubule dynamics was next investigated. Live time-lapse imaging was carried out on type A and B cells expressing GFP-tubulin so that the dynamic behaviour of the microtubules could be analysed. Microtubule length changes were analysed and microtubules were scored as shrinking, growing or pausing and the results shown in Figure 2 below A: low level of MAPX expression B: high level of MAPX expression 0 - Growing Shrinking Pausing Figure 2. Live time-lapse imaging was carried out for 3 minutes on GFP-tubulin expressing A (low MAPX, grey bars) and B (high MAPX, black bars) cells. Changes in microtubule length was analysed and the microtubules were scored every 3 seconds as growing, shrinking or pausing. A total of 100 microtubules were analyses for each cell type and the percentage of microtubules present in each state are shown in the histogram. (d) Explain the time-lapse results and discuss the effect of MAPX on microtubules in terms of dynamic instability. [10 marks] Further studies on MAPX revealed that it localised along the length of microtubules in fixed cells. (e) Which technique would have been used to visualise MAPX along the microtubules? [2 marks] (f) Briefly describe what the technique involves. [6 marks] END OF SECTION B START YOUR ANSWER TO THE NEXT SECTION IN A NEW BOOKLET Section C begins on next page/...

9 9 SECTION C: ESSAY QUESTION Answer ONE question 27. Answer BOTH parts (a) and (b). (a) Describe the Wnt signaling pathway. [20 marks] (b) Discuss two examples of where this pathway plays important roles in development. [10 marks] 28. Answer BOTH parts (a) and (b). (a) Describe the main phases of mitosis emphasising the importance of cell cycle control by cyclins/cdks. [20 marks] (b) Briefly discuss the three types of microtubule involved in chromosomal separation during cell division. [10 marks] 29. Answer BOTH parts (a) and (b). Cells interact with other cells through a number of different junctional and nonjunctional molecules. (a) Give a brief description of two different types of junctional interactions and one non-junctional interaction. [15 marks] (b) In certain pathological conditions cell-cell interactions are disrupted. Discuss two such examples including the functional consequences of such disruption. [15 marks] END OF PAPER

10 10 UNIVERSITY OF EAST ANGLIA School of Biological Sciences May/June UG Examination CELL BIOLOGY BIO-2B06 Registration Number SECTON A: Answer Grid (for Multiple Choice Questions only) Place a single cross in the appropriate box Question No. A B C D E Marks given Marks available

11 11 BIO-2B06 EXAMINATION MARKERS [Do not print this when printing to take to Examinations Office! This is for our information only.] Question No. 1 st Marker 2 nd Marker Section A Q1 Dr G Wheeler Dr J Gavrilovic 25 Section B Q26 Dr M Mogensen Dr M Hajihosseini Section C Q27 Dr G Wheeler Dr M Hajihosseini Section C Q28 Dr A Chantry Dr E Poschl Section C Q29 Dr J Gavrilovic Dr A Chantry