Microbiology Test 3

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Microbiology Test 3
2011-11-05 22:22:50
Micro Test

Micro Test 3
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  1. What is is called when the H-bonds between two DNA strands break?
    Denaturation or melting
  2. Because of ...............one strand of DNA can always be used as the template for the synthesis of another.
    base-pairing rules
  3. What three types of RNA is DNA transcribed to?
    mRNA, tRNA, rRNA
  4. This type of RNA is simply amessenger and it is always translated to give a protein product
  5. This RNA plays a very important role in thetranslational function of the ribosome
  6. This RNA binds to amino acids anddelivers them to the ribosome where the polypeptide chain (that will fold intoa protein) is being translated from the mRNA code
  7. Only mRNA, but not rRNA or tRNA
    A. is composed of ribonucleotides.
    B. serves a functional purpose within the cell.
    C. is translated to form protein product.
    D. is formed when DNA is transcribed
    e. all of the above
    C. is translated to form protein product.
    (this multiple choice question has been scrambled)
  8. Replication of a circular chromosome or a plasmid always begins ata point on the plasmid called the............and can proceed in..............
    origin of replication, both directions
  9. Replication of the E. coli chromosomea. initiates when an RNA polymerase enzyme called Tusunwinds a short stretch of DNA.
    b. originates and terminates at the same location.
    c. results in the transient formation of a region of newlysynthesized DNA called the replication bubble.
    b. originates and terminates at the same location
  10. Before replication begins...........unwind the helix and..............relieve the tension.
    helicases, topoisomerases
  11. At the replication fork, a single complex called the............(containing DNA polymerases) synthesizes both the leading and lagging strands.
  12. DNA polymerase can only synthsize DNA in the..............direction.
    5' to 3'
  13. This enzyme is used to form small RNA primers in the first step of the synthesis of the lagging strand.
  14. DNA polymerase requires a............in order to beigin synthesizing DNA.
    RNA primer
  15. Which of the following is/are true about DNAreplication?a. It starts at the origin of replication.
    b. It is bidirectional
    c. It requires an RNA primer to get started.
    d. It is semiconservative.
    e. All of the above.
    e. All of the above
    What is the sequence of the RNA transcript for the portion ofthe gene shown here?
  17. RNA always looks like the..............strand of DNA except...........is replaced by............
    coding, T, U
  18. The..........is the transcription initiation site.
  19. In prokaryotes,there is often more than 1 gene under control of the same promoter.This is called an
  20. Promoters are consensus sequences of nucleotides that lie..............of the gene
  21. The...................is the subunit of...............that recognizesthe promoter
    sigma factor, RNA polmerase
  22. Which of the following is/are involved with theinitiation phase of transcription but not with elongation ortermination?
    a. RNA polymerase
    b. the sigma factor
    c. the promoter
    d. the hairpin loop
    e. both b and c
    f. both a and d
    • e. both b and c
    • RNA polymerase is used in elongation and the hairpin loop is used in termination.
  23. (T or F) RNA polymerase requires a primer in order tobegin transcription
  24. (T or F) A DNA template strand can betranscribed by more than one RNA polymerase enzymes ata time.
  25. Which terminal of the mRNA transcript is readily available while transcription is still taking place (the 5' or the 3')?
  26. What are the two types of termination?
    Termination due to hairpin loop formation and Rho-dependent termination
  27. Which statement/s regarding prokaryotic translationis/are TRUE?
    a. Only the coding region of an mRNA transcript istranslated to make protein.
    b. The codons UUU, UUC and UUA all encode for the sameamino acid.
    c. More than one codon specifies the amino acid Val.
    d. all of the above
    e. a and c
    e. a and c
  28. Where does translation occur?
  29. tRNA's can recognize more than one codon. This is called..........
  30. What is the Shine-Dalgarno sequence?
    Ribosome binding site
  31. The ribosome binding site is typically............................from the start codon.
    7 nucleotides upstream
  32. Which one of the following correctly summarizesthe order of events that take place during the elongationphase of translation?
    1. The initiating tRNA carrying the f-Met residue is boundin the P-site.
    2. The ribosome advances the distance of one codon alongthe mRNA and the initiating tRNA + f-Met leave throughthe E-site.
    3. The f-Met residue is covalently bound to the amino acidcarried by the tRNA in the A-site.
    4. A tRNA carrying the amino acid that corresponds to thesecond codon binds to the A-site.
    A. 1, 2, 3, 4
    B. 1, 3, 4, 2
    C. 4, 1, 3, 2
    D. 1, 4, 3, 2
    B. 1, 3, 4, 2
    (this multiple choice question has been scrambled)
  33. In which direction is the polypeptide chainsynthesized?
    a. from the carboxyl terminal to the aminoterminal.
    b. from the amino terminal to the carboxylterminal.
    a. from the carboxyl terminal to the aminoterminal
  34. Which of the following is / are involved in replication?
    A. The promoter
    B. DNA polymerase
    C. The Aminoacyl(A)-site
    D. RNA polymerase
    E. sigma factor
    B. DNA polymerase
    (this multiple choice question has been scrambled)
  35. Which statement about eukaryotic and prokaryoticgene expression is FALSE?
    a. In eukaryotic cells only, the 5’ end of the mRNAtranscript is “capped” by the addition of a methylatedguanine derivative.
    b. In eukaryotic cells more often then prokaryotic cells,approximately 200 adenines are added to the 3’ end of themRNA transcript.
    c. Generally only eukaryotic genes have both coding(exons) and noncoding (introns) regions.
    d. Only prokaryotic mRNAs must be transported out ofthe nucleus before they can be translated.
    e. eukaryotic mRNAs are usually monocistronic whereasprokaryotic mRNAs can be either monocistronic orpolycistronic.
  36. A gene that is always expressed is...............
  37. What is an operon?
    A promoter, in prokaryotes, that controls more than 1 gene.
  38. A................blocks transcription by binding to an operator.
  39. A(n)..............facilitates transcription by binding to an activator binding site.
  40. What is a corepressor?
    A molecule that a repressor sometimes requires must be bound to it before it can bind to the operator site.
  41. What is an inducer? Give an example.
    A molecule that binds to the repressor to keep it from binding to the operator site. Example: lac operon
  42. What are two mechanisms by which the genotype of an organism can change?
    mutation and selection
  43. What is a neutral mutation?
    A mutation that codes for a simliar enough amino acid that the overall outcome is not affected.
  44. What is a base substitution?
    Incorporation of an incorrect base
  45. What does the addition or removal of a nucleotide lead to?
    Frameshift mutations, often are null or knockout mutations
  46. What are transposons?
    They disrupt the gene into which they insert
  47. What do alklylating agents do?
    Add methyl groups to bases causing mispairings. Example: nitrogen mustard
  48. What are base analogs?
    They resemble a base so closly that they are incoporated into DNA insted of the normal base. Example: 5-bromouracil
  49. What are intercalating agents?
    They insert between adjacent base pairs. Often leads to the addition of an extra nucleotide and frameshift mutation. Example: Ethidium bromide
  50. What three ways can mutants be detected?
    • 1) observation if they cause a visible change in phenotype
    • 2)By direct selection if the mutant will grow in the prescence of some substance that the wild type cells will not grow in (ex: streptomycin resistant mutants)
    • 3)By indirect selection if the mutant is an auxotrophic mutant and needs something for growth that the prototrophic cells do not need.
  51. An organism that is Trp
    A. will grow on a GSA plate.
    B.is unable to synthesize the amino acidtryptophane.
    C. has a trp+ genotype.
    D. is a prototroph
    D. is a prototroph
    (this multiple choice question has been scrambled)
  52. What does the Ames test do?
    Identifies potentila carcinogens by testing chemicals for their ability to cause mutation in a bacerial system. Particular system used is His-auxotroph of Salmonella
  53. A student doing his summer internship at RockyMountain Labs, performs the Ames Test on a chemicalthought to be a potential carcinogen. After incubating theGSA plate, the student notes that there are many morecolonies on the plate than are seen on a negative controlplate. Which conclusion/s does the student make?
    a. The chemical tested is a potential carcinogen.
    b. The chemical tested is not a potential carcinogen.
    c. The chemical tested is a mutagen.
    d. The chemical tested is not a mutagen.
    e. a and c
    f. b and d
  54. What are the three mechanisms of lateral gene transfer?
    transformation, transducation, conjugation
  55. What is a recombinant cell?
    When an exogenote becomes a stable part of the recipien's genome.
  56. Transformation, transduction and conjugation
    a. all involve a horizontal gene transfer.
    b. all involve an F-pilus.
    c. all require cell-to-cell contact.
    d. all involve a bacteriophage.
    e. a and b
    f. a, b and c
  57. Which statement/s describe/s DNA-mediatedtransformation?
    a. The uptake of “naked” DNA. The DNA can be either aplasmid or a linear piece of DNA.
    b. A horizontal gene transfer.
    c. The transfer of DNA from one cell to another by abacteriophage.
    d. The process by which a cell is transduced.
    e. a and b
    f. b and c
  58. Which statement/s about DNA-mediatedtransformation is/are FALSE?
    a. DNA-mediated transformation involves the uptake of eitherlinear or plasmid, naked DNA.
    b. A cell that is capable of being transformed is termed acompetent cell and although a few genera of bacteria arenaturally competent, most must be made competent usingeither a chemical treatment or electroporation.
    c. During transformation of a bacterial cell with a linearfragment of DNA, the fragment of donor DNA sometimesreplaces a stretch of the recipient’s chromosome in twoconsecutive steps termed breakage and reunion.
    d. During transformation of a bacterial cell with a linearfragment of DNA, a single-stranded DNA molecule istransferred from the donor to the recipient cell via the F pilus.
  59. If plasmid DNA is taken up by the cell during transformation, then the plasmid remains in the...............and replicates....................
    cytoplasm, independently
  60. What is entry?
    A double-stranded piece of DNA adheres to the cellsurface. One strand is degraded by nucleases and the other strandenters the cell. This mechanism varies amongst different genera.
  61. What is integration?
    ThessDNA aligns with a region on the recipient cell’s chromosome towhich it is highly homologous. (**HIGHLY HOMOLOGOUS =VERY SIMILAR). The recipient DNA separates and pairs with thedonor DNA. A nuclease cleaves the recipient cell’s DNA andreleases the homologous section into the cytoplasm to be degradedby nucleases. This is called BREAKAGE. The donor DNA nowreplaces the recipient DNA = REUNION. This forms a region ofheteroduplex DNA (one strand is donor DNA, the other isrecipient DNA).
  62. After donor DNA has integratedinto the recipient cell’s chromosome, is stable transformation alwaysaccomplished? Why?
    not always, sometimes the mismatchrepair system catches errors and the sequence is unchanged. There’sa 50/50 chance in terms of which strand will be repaired.
  63. During..................a bacteriophage (termed adefective phage) accidentally packages bacterial DNA into its capsidhead rather than phage DNA.
    generalized transduction
  64. Which statement about generalized transduction isFALSE?
    a. During generalized transduction, an error is made duringthe phage lysogenic life cycle. This error allows the phage totake a few specific bacterial genes, next to the point ofintegration, when it leaves the host chromosome.
    b. During generalized transduction, any gene of the donor can be transferred to the recipient.
    c. During generalized transduction, a phage is mistakenlypackaged with bacterial DNA.
    d. During generalized transduction, a defective phage is formed. This defective phage will effectively transfer genes from a donor cell to a recipient.
  65. What is conjugaion?
    The transfer of DNA from a donor to a recipient cellvia cell-to-cell contact.
  66. Which one of the following is the most important means of plasmid transfer?
    A. Transformation
    B. Translocation
    C. Transduction
    D. Conjugation
    D. conjugation
    (this multiple choice question has been scrambled)
  67. Cells that are F+ contain the............plamid.
  68. The F- plasmid encodes for what? What is its purpose?
    The F pilus which serves as a bridge over which the F plasmid can be transferred from the donor cell to the F-(recipient cell). Always unidirectional and only the plasmid is transferred.
  69. What are the steps of conjugation?
    • 1. contact
    • 2. mobilization
    • 3. transfer
    • 4. synthesis
  70. The F (fertility) plasmid
    a. is transferred during a lateral gene transfer event called conjugation.
    b. can be found only in male (donor) cells.
    c. is self-transmissible and codes for the synthesis of astructure called the F pilus.
    d. all of the above
    e. only a and c
  71. In lab, we worked with a strain of Staphylococcus aureus that was resistant to penicillin. Which one of thefollowing would probably be seen in this strain of S. aureus?
    a. gas vesicles
    b. an R plasmid
    c. a lysogenic bacteriophage
    d. a lytic bacteriophage
    e. none of the above
  72. Hfr cells
    a. are cells in which the F plasmid has become integrated into the chromosome.
    b. can transfer part of their chromosome to arecipient cell. After this transfer the recipient cell will become F+ and will also be capable of transferring its chromosome.
    c. are always cells that have more than one Rplasmid.
    d. have a higher propensity to take up plasmid DNA
  73. An antimicrobial drug
    a. is a chemotherapeutic agent.
    b. is any chemical used to treat microbial infection.
    c. that has a high therapeutic index is selectively toxic
    d. all of the above.
  74. Beta-lactam drugs
    a. are most commonly thought to inhibit the enzymes responsible for forming the tetrapeptide chains betweenstrands of peptidoglycan.
    b. contain a beta-lactam ring that is essential for activity.
    c. include the penicillins and the cephalosporins.
    d. are effective only when cells are actively growing.
    e. are naturally more effective on Gram-positive cells.
    f. generally have very few side effects.
    g. all of the above
    h. only a through c
  75. The broad-spectrum penicillins
    a. are effective against both Gram-positive and Gramnegativeorganisms.
    b. are isolated directly from Penicillium chrysogenum andundergo no further modification.
    c. include penicillin G and Penicillin V.
    d. include ampicillin and amoxicillin.
    e. a and d
    f. b and c
  76. The extended-spectrum penicillins
    a. are partially synthetic.
    b. are the cephalosporins.
    c. include cephalexin.
    d. are effective against some tough Gram-negative bacterialike Pseudomonas.
    e. a and d
    f. b and c