GENERAL MICROBIOLOGY EXAM2

Answer questions 17, 18, 19, 20, 21, 26, 31, 37GENERAL MICROBIOLOGY EXAM2A FALL 2013 READ THE PROBLEM! 1. You assay three toxins for level of toxicity. Toxin X has an LD50 of 1 mg, toxin Y of 0.05 mg and toxin Z of 0.0001 mg. Which one is the most toxic? A. Toxin X B. Toxin Y C. Toxin Z D. None are toxic E. They are the same 2. Your patient is extremely sick, may die but does not have a fever. You are told he/she ingested a toxin. Based on the signs, what kind of toxin do you think it might be? A. Endotoxin B. Enterotoxin C. Exotoxin 3. Which of these is NOT a property of diphtheria toxin? A. Is an AB toxin D. Disrupts protein synthesis E. This toxin has all of these B. Its gene is carried on a phage C. ADP?ribosylates elongation factor 2 4. Which of these is NOT a property of cholera toxin? A. Is an AB toxin D. mimics a mammalian hormone B. Converts ATP to ADP E. this toxin has all of these C. Causes secretion of HCO3? into the intestinal lumen 5. Which of the following is not a PAMP? A. Flagellin C. LPS E. They all are PAMPs B. Flagella D. Teichoic acid 6. You perform a Kirby Bauer test, and interpret your data based on the following table (where AB = antibiotic): Sensitive AB Resistant Intermediate 1 12 or less 13?14 15 or more 2 9 or less 10?13 14 or more 3 14 or less 15?16 17 or more All of your data are the same : 14 mm. Which antibiotic can you use? A. 1 B. 2 C. 3 D. All of them E. None of them 7. In the above question what do you measure for the data? A. Optical density C. Dilution series E. Concentration B. Growth rate D. Zone of inhibition 8. You are trying to ID an isolate in your lab and perform an oxidase test. You smear a colony on a test strip, and in 10 seconds it turns dark purple black. The test is positive (it produces oxidase) . This test is: A. Selective B. Differential C. Both A and B D. Neither 9. You do an antibody titration on yourself after you return from a vacation at a place where an outbreak of diphtheria occurred. What do you analyze from yourself to do the analysis? A. Blood B. Serum C. Sputum D. Stool E. Skin swab 10. In the above question you detect antibodies to diphtheria. You should: A. Check into a hospital C. Get a vaccination B. Repeat the test in a few days D. Nothing 11. Phagocytes are important in which type(s) of immunity? A. Adaptive B. Innate C. Both A and B D. Neither 12. A bacterial cell with lambda integrated into its chromosome is a: A. Phage B. Prophage C. Virus D. Lysogen E. Virion 13. What determines the lytic vs. lysogenic cycle of lambda? A. Accumulation of Cro D. All of the above B. Accumulation of cI E. None of the above C. Accumulation of cII 14. What does the product of the lambda gene cIII do ? A. Inserts lambda into the host chromosome D. Turns on cro B. Turns on cI E. Turns off cI C. Stabilizes cII 15. What does the CRISPR system recognize? A. RNA viral sequences D. All of the above B. DNA viral sequences E. None of the above C. Palindromic sequences 16. In the CRISPR system what actually cuts viral NA? A. RecA D. Reverse transcriptase B. CAS proteins E. Ligase C. Endonuclease 17. What type of genetic recombination involves uptake of free DNA in the environment? A. Transduction C. Transformation E. B and C B. Transfection D. Translation 18. An E. coli strain is “Hfr”. What does it have? A. Hfr in the chromosome C. The plasmid F+ B. F in the chromosome D. The plasmid F? 19. Nutrient agar with ampicillin and XGal is commonly used to screen for insertion of genes into E. coli using pUC19. Colonies that grow on this will be either clear or blue. You attempt to insert the new gene X with pUC19. Which colonies have the new gene and why? A. Blue, because they are ampicillin resistant B. Blue because they have the intact lacZ gene C. White because they are ampicillin resistant D. White because they have the intact lacZ gene E. None of the above 20. In the above question, if you were successful in cloning the gene where is the new gene? A. In the E. coli chromosome D. In the medium B. In a plasmid inside E. coli E. On the plate C. In lambda 21. In transformation: A. SS DNA binds to the cell surface and is brought in B. DS DNA binds to the cell surface and is brought in C. DS DNA binds to the cell surface and one strand is brought in D. All of the above can occur 22. A restriction enzyme will produce gene fragments with sticky ends when it: A. Cuts both strands directly opposite each other B. Cuts both strands at points that are staggered C. Only cuts one strand, the sticky one D. Cuts RNA 23. In the above question, what is used to insert the gene fragment into another genome? A. DNA ligase D. A and B B. A new restriction enzyme E. A and C C. The same restriction enzyme 24. What is the smallest known pathogen? A. A virus B. A prion C. A viroid D. A plasmid 25. What infective agent is pure protein? A. A virus B. A prion C. A viroid D. A plasmid 26. After you have carried out replica plating, what would be a colony of interest that you might select to start a new culture? A. One present on both the minimal plate and the control plate B. One present on the minimal plate but not the control plate C. One present on the control plate but not the minimal plate D. One present on the master plate E. Any colony that grows on any plate 27. PrPSC is different from PrPC in what way(s)? A. It has more alpha helices D. It converts PrPC to a new form B. It has more beta sheets E. All but A C. It aggregates 28. What type of nucleic acid is never found in viruses? A. SS DNA B. SS RNA C. DS DNA D. DS RNA E. None of the above 29. Which of the following is not carried out by reverse transcriptase? A. Synthesis of DNA from an RNA template B. Acts as a ribonuclease to degrade RNA from an RNA/DNA hybrid C. Synthesis of DNA from a DNA template D. All of the above are carried out E. None of the above are carried out 30. The Ames test will tell you if a chemical is: A. Carcinogenic B. Mutagenic C. Both of these 31. In the Ames test a positive result would be: A. Lots of cells growing around the test filter disc B. No cells growing around the test filter disc C. Lots of cells growing around the control filter disc D. No cells growing around the control filter disc E. The same # of cells growing around the test and control discs 32. In the above question, what is on the test disc? A. An antibioticD. A plasmid B. A suspected mutagen E. Nothing C. A suspected carcinogen 33. Why do bacteria usually modify their own DNA by methylation? A. It is easier to replicate D. To use as mRNA B. So RecA can recognize it E. To prevent unwinding C. So its own restriction enzymes don’t cut it 34. Viral + RNA can be recognized by the host as: A. DNA B. tRNA C. rRNA D. mRNA E. ? RNA 35. What causes antigenic shift? A. The presence of a segmented genome B. Accumulation of random mutations over time C. A change in virion surface properties D. Selection by the host E. A plasmid 36. What type of virus has a tegument? A. All viruses C. Pox virus E. Rhabdovirus B. Herpesvirus D. Retrovirus 37. Which of the following is not carried out by RecA? A. Binds to SSB B. Displaces one strand of DNA C. Helps in homologous recombination D. Nicks DNA E. Forms a complex with new and old DNA 38. ??lactam antibiotics work by: A. preventing the precursors of peptidoglycan from moving out of the cell B. preventing bond formation between –D?Ala and –D?Ala C. preventing bond formation between –D?Ala and –DAP D. binding to 16S rRNA on the 30S subunit E. cleaving the ??lactam ring 39. What do autolysins do? A. lyse the cell so viruses can exit C. lyse themselves B. lyse peptidoglycan during cell division D. lyse autos 40. Why is clavulonic acid often given together with ampicillin? A. It is another antibiotic with a different target B. It prevents efflux of ampicillin C. It prevents ??lactamase from cleaving a ??lactam ring D. It stabilizes ampicillin E. It opens the porins so ampicillin can enter the pathogen