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 FUNDAMENTALS OF MOLECULAR BIOLOGY AND GENETICS BIO-4003A 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. Semi-log graph paper is provided. Notes are not permitted in this examination. Do not turn over until you are told to do so by the Invigilator. BIO-4003A Module Contact: Professor Kay Yeoman, 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. Which mutagenic agent was used to induce mutations in the rii gene of bacteriophage for studies on the genetic code? a) Proline b) Proflavin c) Difalvin d) Triflavin e) Flavin mononucleotide 2. Which of the following RNA molecules contains modified nucleotide bases? a) mrna b) rrna c) trna d) mirna e) snrna 3. The wobble hypothesis states that: a) perfect complementarity is required between a codon and its anticodon b) only one complementary base is required between the codon and anticodon c) the first base in the anticodon can vary d) the middle base in the anticodon can vary e) the third base in the anticodon can vary 4. Which of the following DNA sequencing technologies uses templates immobilised on microscopic beads? a) Illumina b) Pacific Biosciences c) ABI 373 d) Helicos e) 454 Section A continues on next page/...

3 3 Section A continued Escherichia coli cells can be made competent (able to take up DNA) by treatment with a solution of: a) Calcium chloride b) Lithium chloride c) Potassium carbonate d) Sodium azide e) Sodium phosphate 6. For crystalline DNA, how many base pairs are there in one turn of the helix? a) 0.1 b) 1 c) 4 d) 10 e) What is found at the 5 end of a DNA strand? a) Phosphate group b) Polymerase c) Hydroxyl group d) Uracil e) DNA has no ends 8. Which of these is true of DNA replication in prokaryotes and eukaryotes? a) It is conservative and continuous on both strands b) It is conservative and discontinuous on both strands c) It is semi-conservative and continuous on both strands d) It is semi-conservative and discontinuous on both strands e) It is semi-conservative and continuous on one strand and discontinuous on the other strand Section A continues on next page/... TURN OVER

4 4 Section A continued Which polymerase removes the RNA primers of Okazaki fragments during DNA synthesis in E. coli? a) DNA polymerase I b) DNA polymerase II c) DNA polymerase III d) DNA polymerase IV e) Helicase 10. Telomerases are composed of: a) DNA and RNA b) DNA and protein c) RNA and protein d) Lipid and protein e) Lipid and DNA 11. A mutation that involves one pyrimidine base being changed to another pyrimidine base (e.g. C to T) is called a: a) transcription mutation b) transition mutation c) translation mutation d) transversion mutation e) transposon mutation 12. Yeast two-hybrid experiments can reveal: a) two mrna molecules which interact b) two yeast strains which interact c) two complementary DNA strands which interact d) two proteins which interact e) none of the above 13. Which of the following is not an example of a post-translational protein modification? a) Formation of a disulfide bridge b) Addition of a heme group c) Removal of a signal peptide d) Phosphorylation of a tyrosine residue e) Peptidyl-proline cis-trans isomerization Section A continues on next page/...

5 5 Section A continued Proteins targeted to the endoplasmic reticulum (ER): a) have an N-terminal signal sequence b) possess an ER-binding domain c) possess a domain with ATPase activity d) are stable at high temperatures e) are never glycosylated 15. The fluorophore of Green Fluorescent Protein is formed by: a) addition of fluorine to a tyrosine residue in a cyclic dipeptide b) addition of fluorine to a tyrosine residue in a cyclic tripeptide c) cyclization of a tyrosine-containing dipeptide d) cyclization of a tyrosine-containing tripeptide e) deprotonation of a tyrosine residue within the β-barrel structure 16. Transcription is the process by which: a) protein is generated from a mrna template b) mrna is generated from a DNA template c) DNA strands are replicated d) DNA enters a bacterial cell e) viruses infect cells 17. The termination of transcription in bacteria can utilise: a) Rho protein b) Sigma factor c) Gamma carboxylase d) Beta galactosides e) Alpha helices 18. Which of the following processes contributes to the reassortment of genetic information in meiosis? a) Meiosis division II b) Independent assortment c) Anaphase II d) S phase e) G1 and G2 phases Section A continues on next page/... TURN OVER

6 6 Section A continues on next page Which of the following karyotypes describes the aneuploidy associated with the most common form of Down Syndrome? a) 45, -22 b) 47, +22 c) 46 d) 45, -21 e) 47, Which of the following is a genome editing technology that uses a single-guide RNA? a) ZFNs b) TALENs c) EcoRI d) ClaI e) CRISPR For all remaining questions in Section A, please use an answer booklet. Remember to attach your multiple choice answer grid to the booklet. 21. What is the conformational change that is induced in AraC by the binding of arabinose and how does it effect transcription of the arac and arabad genes? [5 marks] 22. The chromosomal basis of sex determination in flies and humans is similar (i.e. females are XX and males XY) but how do the molecular mechanisms differ? [5 marks] 23. Explain why each of the following is required in plasmids that are used in cloning experiments: (a) antibiotic resistance genes; (b) origin of replication; (c) polylinker region. [5 marks] 24. How does Agrobacterium tumefaciens transfer foreign genes into plants? [5 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 this question [30 marks] 25. A plasmid named pbio was cut with the restriction enzymes shown in Table 1 below and the fragments obtained were analysed using DNA agarose gel electrophoresis. Using a standard curve of known DNA fragment sizes you were able to ascertain the size in kb of the digested fragments. These are given in Table 1. Restriction enzyme Fragment size(s) in kb EcoR1 8 Pst 1 8 Sal1 6; 2 Pst1;Sal1 6; 1;1 EcoR1; Sal1 3; 3; 2 EcoR1; Pst1 4;4 EcoR1; Pst1; Sal1 3;3;1;1 Table 1. DNA fragment sizes (kb) of pbio cut with a combination of single, double and triple digests (a) Using the information in Table 1 place the restriction enzyme sites on a plasmid map and mark the distance between each site in kb. [8 marks] (b) What is the size of the plasmid in Kb? (c) The pbio plasmid contains an antibiotic resistance gene for the antibiotic tetracycline. What is the function of this gene in the transformation of pbio into a host bacterial cell? [4 marks] The plasmid pbio also encodes a hydrophobic protein which was purified by hydrophobic interaction chromatography (HIC). The mass of the purified protein was then determined using SDS-PAGE, the protein standards are provided in table 2. Mass of Protein Standard (kda) Distance migrated (mm) Table 2. Distance migrated (mm) of protein mass standards (kda) Section B Q25 continues on next page/... TURN OVER

8 8 Section B Q25 continued... (d) Explain why HIC was a suitable method for the purification of this protein. [5 marks] (e) Draw a graph of distance migrated against protein molecular mass using the information in Table 2. [10 marks] (f) The purified protein from pbio migrated a distance of 12 mm, using your graph from part e, determine a mass in kda for the protein. [2 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 [30 marks] 26. Using labelled diagrams illustrate the major differences in chromosome behaviour for two sets of homologous chromosomes at the various stages of mitosis and meiosis. One consequence of meiosis is the reassortment of genetic variation into new combinations in eggs and sperm. Describe the two processes that facilitate this reassortment. 27. Answer BOTH parts (a) and (b). (a) Draw and label a diagram of an E. coli replication fork. Show the parental and daughter molecules for both the leading and lagging strands, label all 5 and 3 ends, and show the main proteins involved in DNA replication. [20 marks] (b) What enzyme activity is exhibited by primase (DnaG in E. coli) and what critical function does it fulfil during replication? [10 marks] 28. How do proteins fold in the cell? Include in your answer an explanation of at least one molecular system which is responsible for assisting misfolded proteins in achieving their native state. How might protein misfolding lead to disease? END OF PAPER

10 Registration Number UNIVERSITY OF EAST ANGLIA School of Biological Sciences Main Series UG Examination FUNDAMENTALS OF MOLECULAR BIOLOGY AND GENETICS BIO-4003A SECTION 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