Microbiology 301
Second Midterm Exam
You will be given an examination and a computer answer sheet. Make sure your name is on both the question and answer sheet. MARK ANSWER ON BOTH AND HAND BOTH IN.
The COMPUTER SHEET WILL NOT BE RETURNED and you are RESPONSIBLE for the correct transfer of your answers to the computer answer sheet.
The questions will be returned along with an individual student score report in a room in the laboratory area (number to be announced). If you wish to have your examination returned privately, give the proctor of the examination a note to that effect.
Choose the ONE best answer.
1. Which of the following statements is FALSE?
A. The genotype of a cell is the sum total of all of the genetic
potential of the cell.
B. Not all of the genetic potential of a cell will be expressed under
any given growth environment.
C. For a mutation to be considered a mutation, the change in
nucleotide sequence in a gene must result in a phenotypic change.
D. The mutation rate is the probability that a gene will mutate
during a cell division cycle.
E. The spontaneous rate of mutation of genes within a cell varies,
but it is always the same for a given gene.
2. A tautomeric shift is the irreversible change in structure of one of the nitrogen-containing bases of DNA as a result of re-distribution of its electrons/protons, which changes the base-pairing rules of that base.
A. True
B. False
3. Which of the following statements is FALSE?
A. Mutations are essential to the long term survival of the
species.
B. The proof-reading ability of DNA polymerase reduces the number of
errors/ mutations, committed during DNA replication.
C. Exposure of cells to mutagenic agents increases the probability of
introducing mutation into genes.
D. Chemical mutagens show specificity with respect to the gene that
they can mutate.
E. A chemical mutagen, such as the deaminating agent nitrous acid,
manifests its effect following DNA replication.
4. Which of the following statements about DNA repair mechanisms is FALSE?
A. Light repair can only repair thymine dimer damage.
B. Cells exposed to UV light, and immediately placed in the dark
would be able to repair UV damage.
C. Dark repair involves "cutting" out of the damaged DNA region by
DNA polymerase.
D. Dark repair requires DNA polymerase and ligase, two enzyme
involved in DNA replication.
5. Which of the following statements is/are TRUE?
1. UV light is mutagenic because it causes the formation of
thymine dimers, which distorts the 3-dimensional structure of DNA,
and this interferes with DNA replication and transcription.
2. Intercalating agents cause the covalent linkage of both strands of
the DNA molecule.
3. Insertion sequences are mutagenic because they can insert
themselves into a gene, thus destroying the integrity and function of
that gene.
4. A nonsense mutation in a gene results in one amino acid being
substituted for another in the protein encoded by that gene.
5. The addition or removal of one or two bases in a gene is
potentially more detrimental than one that adds/removes 3 bases.
A. 1, 3, 5 B. 2, 3 C. 1, 2, 4 D. All of the above
6. Adding penicillin to a medium increases the mutation rate of the gene that determines penicillin resistance.
A. True
B. False
7. Which of the following statements about the Ames Test is TRUE?
A. It determines which chemicals are carcinogenic.
B. It determines how well bacteria, specifically Salmonella, repair
DNA damage.
C. It determines the presence of carcinogens in rat livers.
D. It measures the carcinogenic potential of a chemical by
determining how mutagenic the chemical is.
8. Which of the following statements about bacteriophage is FALSE?
A. They are all obligate intracellular parasites.
B. They contain only one type of nucleic acid, either DNA or RNA;
never both.
C. Their genome is always surrounded by a protective protein coat
called a capsid structure.
D. Many phage have segmented genomes.
E. Only the phage genome enters the infected cell.
9. Bacteria of the genus Rickettsia and Chlamydia differ from other eubacteria in their ability to continuously make phage particles throughout their growth cycle without being killed.
A. True
B. False
10. RNA phage replicate using host RNA polymerase.
A. True
B. False
11. The replica plating technique is used to isolate auxotrophic mutants. Using the following diagram, which colony(ies) are tryptophan auxotrophs ?
A. 1 through 9
B. 1 and 6
C. 2, 3, 5, 7, 9
D. 4 and 8
E. 1, 4, 6, 8
12. Which of the following statements about phage replication is FALSE?
A. The burst size of a phage infection is always about 200
particles per cell.
B. During the eclipse period, no intracellular infectious phage
particles are present.
C. The latent period is the time from when cells were infected to the
time when phage particles are being released from cells.
D. Release of phage, in most cases, is by cell lysis.
13. Which of the following statements is FALSE?
A. The presence/absence of chemical receptors on cells determines
the host range of a virus.
B. A bacterial species may be infected by different
bacteriophage.
C. Bacteriophage T4 has the ability to degrade host DNA, but not its
own DNA.
D. In the case of ss-DNA phage, replication of the phage genome goes
through a ds-DNA intermediate.
E. Infection by a specific ss-DNA phage results in progeny phage that
contain either "plus" or "negative" ss-DNA.
14. Which of the following statements is FALSE?
A. A temperate bacteriophage has the ability to undergo
lysogeny.
B. A prophage is a phage genome that is part of the cell's chromosome
structure.
C. A cell that harbors a prophage is "immune" to infection by the
same phage.
D. A lysogenic cell is actively producing phage particles.
E. Lysogenic conversion is responsible for the pathogenicity of
certain bacteria.
15. Which of the following statements about restriction enzymes is FALSE?
A. They are naturally produced by bacteria.
B. Many different types/specificities are commercially available.
C. Different restriction enzymes recognize and cut at different
sites.
D. Restriction enzymes are used in cloning AND Southern blots.
E. The name of the enzyme is derived from the name of the person who
discovered the enzyme.
16. Which of the following best describes the function of a cloning vector?
A. It serves as a replicating carrier of foreign DNA.
B. It causes bacterial cells to take up DNA from the environment.
C. It cuts DNA at specific sites.
D. It allows bacteria to synthesize specific restriction enzymes.
E. It causes DNA to denature.
17. Which of the following best describes the function of a DNA probe?
A. It causes sticky ends to anneal.
B. It forms a covalent bond between sticky ends.
C. It seeks out complementary DNA.
D. It creates more copies of a specific piece of DNA.
E. It cuts DNA at specific sites.
18. Which of the following about cloning is FALSE?
A. The recombinant DNA molecule is introduced into a new cell by
transformation.
B. An antibiotic such as ampicillin is used to inhibit cells that
have not successfully taken up the recombinant DNA.
C. Most chromosomal DNA fragments generated by digesting the DNA with
a restriction enzyme have an origin of replication.
D. The vector must encode a restriction enzyme recognition site AND a
selectable marker.
19. A Southern blot can be used to detect all of the following EXCEPT:
A. Whether or not a gene is being expressed.
B. The presence/absence of a specific DNA sequence.
C. The size of restriction fragment that encodes a particular DNA
sequence.
D. Differences in chromosomal sequences (i.e. strain
differences).
20. Which of the following statements about PCR (polymerase chain reaction) is FALSE?
A. The nucleotide sequences of the primers determine which part of
the DNA is amplified.
B. Taq polymerase is destroyed by high temperature, so it must be
added to the reaction mix after each cycle.
C. One amplification cycle consists of short incubations at three
different temperatures.
D. Small amounts of contaminating DNA can affect the results.
E. It can be used to amplify dinosaur DNA.
21. Keratin is found in which of the following?
A. Skin
B. Respiratory tract
C. Tears
D. Gastrointestinal tract
E. Urinary tract
22. Which of the following would you expect to contain no normal flora?
A. Skin
B. Mouth
C. Large intestine
D. Bladder
E. More than one of the above
23. Opsonization can involves which of the following pairs?
A. Macrophage - antibody
B. B cell - complement
C. T cell - lysozyme
D. Macrophage - lysozyme
E. T cell - neutrophil
24. Which of the following is NOT a characteristic of inflammation?
A. Redness
B. Pain
C. Local heat
D. Fever
E. Swelling
25. Which of the following is NOT an effect of complement activation?
A. Interference with viral replication
B. Bacterial cell lysis
C. Opsonization
D. Enhanced phagocytosis
E. Increased blood vessel permeability
26. Which of the following is TRUE regarding interferon?
A. It causes cells to synthesize an antiviral protein.
B. It promotes phagocytosis.
C. It causes cell lysis.
D. It acts against specific viruses and bactertiophage.
E. It attacks and lyses invading viruses.
Use the following to answer questions 27 through 29.
A. IgA
B. IgD
C. IgE
D. IgG
E. IgM
27. Which class of antibody protects a developing fetus?
28. Which class of antibody that protects against intestinal pathogens?
29. Which of antibody produced first in response to an initial
infection?
30. Specificity of an antibody is due to the...
A. the number of antigen binding sites it has.
B. the H chain only.
C. the L chain only.
D. the constant regions of the H and L chains.
E. the variable regions of the H and L chains.
31. The part of the antibody that is recognized by other immune cells/components (i.e. phagocytes, complement components) is the...
1. Fc region.
2. Fab region.
3. variable region.
4. constant region.
A. 1, 2 B. 3, 4 C. 1, 4 D. 2, 3 E. 2, 3, 4
32. Which of the following is an example of natural passive immunity?
A. Immunity resulting from recovery from an infection.
B. Immunity resulting from injection of a toxoid.
C. Immunity resulting from an injection of an antitoxin.
D. Immunity in a newborn resulting from being breast-fed.
E. Immunity resulting from the production of memory cells.
33. In response to infection, B cells will continually rearrange their DNA until they make an antibody that recognizes the antigen.
A. True
B. False
34. Which of the following about the V, D, and J regions of antibody genes is TRUE?
A. They encode the constant region of the antibody.
B. A single B cell expresses EITHER a V, a D, or a J region, but not
all three.
C. Two B cells that BOTH express V1, D1, and J1 will always produce
the identical antibody.
D. The D region determines the class of the antibody.
E. Different B cells have different DNA in the V, D, and J gene
regions.
35. The function of a CD8 cell is to...
A. stimulate stem cells to become plasma cells.
B. produce cytokines which stimulate appropriate B or T cells to
multiply.
C. differentiate to become plasma cells.
D. enable macrophages to respond to infections more quickly.
E. kill infected "self" cells.
36. A protein that is synthesized by a cell will be "presented" in:
A. MHC Class I
B. MHC Class II
C. CD4
D. CD8
E. CD4 AND CD8
37. HIV infects cells that have which primary function?
A. Presenting exogenously synthesized antigen
B. Presenting endogenously synthesized antigen
C. Killing infected "self" cells
D. Produce cytokines that stimulate appropriate B cells and T cells
to multiply
E. Produce antibody
38. Which of the following is FALSE?
A. Graves disease is due to autoantibodies of the class IgG.
B. Expression of certain MHC types is correlated with some autoimmune
diseases.
C. The chance that a person's MHC types match those of a sibling is
greater than the chance they have the same MHC types as either
parent.
D. You inherit MHC genes from both your mother and your father, but
only one set is expressed.
E. It is likely that no two people in this class have the same set of
MHC types.
39. Which of the following diseases no longer exists because of a successful eradication effort?
A. Smallpox
B. Polio
C. Measles
D. Tetanus
E. Diphtheria
40. Which of the following statements about killed/inactivated vaccines is FALSE?
A. They have led to the decline of several deadly diseases.
B. If properly made, they cannot cause disease.
C. Toxoids are an example of this type of vaccine.
D. They result in production of memory cells.
E. A single immunization is usually all that is necessary for long term protection.
41. All of the following are advantages of attenuated vaccines EXCEPT:
A. They have led to the decline of several deadly diseases.
B. If properly made, they cannot cause disease.
C. In some cases they can be given orally (Sabin vaccine).
D. They result in production of memory cells.
E. A single immunization is usually all that is necessary for long term protection.
Use the following key to answer questions 42 though 44
A. ELISA (enzyme-linked immunoabsorbant assay)
B. Western blot
C. Fluorescent antibody
D. Agglutination
42. Which test is analogous to a technique used in genetic fingerprinting?
43. Which test requires a special microscope?
44. Which test is often used for screening numerous samples?
Use the following key to answer questions 45 through 49. (answers can be used more than once)
A. Transformation
B. Conjugation
C. Generalized transduction
D. Specialized transduction
E. More than one of the above
45. Requires a lysogenic cell
46. Utilizes an F plasmid
47. Only a few very specific genes are transferred.
48. Requires a bacteriophage
49. The donor of the DNA survives the process.