BioSc221/325
Exam 2
Name ______________________________
Multiple choice. (1 point each) Choose the one best answer to each of the following questions.
____ Small protein that associates with bacterial RNA polymerase to facilitate promoter recognition and is released during
transcription.
A. alpha
B. beta
C. gamma
D. sigma
____ Bacterial protein involved in homologous recombination and which is required for repair of UV damage to DNA.
A. helicase
B. topoisomerase
C. repairase
D. RecA
____ Quinolone antibiotics target ____ which is required for restoring supercoiling of newly synthesized DNA.
A. helicase
B. DNA gyrase
C. DNA ligase
D. DNA polymerase
____ UV light is lethal to bacterial cells due to formation of
A. pyrimidine dimers which, when they are removed, can result in double stranded breaks in the DNA.
B. apurinic sites which are easily broken.
C. double stranded breaks resulting from direct cleavage by the UV radiation.
D. creation of multiple nonsense codons that disrupt translation.
____ Plasmids that have a single origin of replication but are capable of replicating in more than one genera are called
A. broad-host range plasmids
B. suicide plasmids
C. shuttle vectors
D. cosmids
____ Which of the following genera does not include endospore producing bacteria?
A. Bacillus
B. Clostridium
C. Sporomusa
D. Staphylococcus
____ Protein involved in transcriptional termination.
A. core enzyme
B. stem loop
C. rho
D. sigma
____ Genes that are expressed at the same level at all times are said to be
A. constitutive
B. inducible
C. repressible
D. activated
____ Most prokaryotic promoters have a two-part consensus sequence that consists of a
A. promoter and terminator
B. promoter and operator
C. activator and operator
D. –10 and –35 region
____ Several genes that are transcribed in the same direction and share the same promoter are called a(n)
A. operator
B. operon
C. polylinker
D. polypromoter
____ Genes encoding the enzymes required for utilization of maltose as a growth substrate are likely to be controlled by what
type of repressor?
A. inducible
B. repressible
C. constitutive
____ Which of the following phenomena is probably not controlled by a quorum-sensing system?
A. colonization of the lung epithelium by Pseudomonas aaeruginosa
B. colonization of the light organ of a flashlight fish by light producing bacteria
C. formation of a biofilm by “slime” producing bacteria
D. chemotaxis
____ In two-component regulatory systems a signal is relayed to the regulator protein by
A. phosphorylation
B. adenylation
C. autoinducer
D. a peptide
____ The antibiotic to the right is a(n)
A. aminoglycoside
B. -lactam
C. chloramphenicol
D. macrolide
E. tetracycline
____ The antibiotic to the right is a(n)
A. aminoglycoside
B. -lactam
C. chloramphenicol
D. macrolide
E. tetracycline
____ Natural transformation does not require
A. membrane associated transport proteins
B. linear double stranded DNA
C. holes in the membrane
D. homologous recombination
____ Which of the following is not a mechanism for horizontal gene transfer in nature
A. conjugation
B. electroporation
C. transduction
D. transformation
____ Resistance to antibiotics that target the ribosome is often obtained by all but which of the following mechanisms?
A. acetylation
B. adenylation
C. phosphorylation
D. methylation
____ Mobilizable plasmids require a self-transmissible “helper” plasmid because they lack which of the following?
A. oriT
B. proteins required to nick the plasmid at its oriT
C. genes that encode the mating bridge
D. antibiotic resistance genes
Matching. (1 point each) Match the definition in the left column with the appropriate term in the right column. Note, not all
terms will be used.
____ The energy source for the phosphotransferase system.
____ Loss of electrons by a compound.
____ Plasmid with more than one origin of replication for use in organisms from two different
kingdoms
____ A plasmid encoded gene used to detect the presence of a plasmid in a host cell.
____ Endospores contain a high concentration of ___ which probably contributes to resistance.
____ Mechanism by which Streptococcus pneumoniae can acquire penicillin resistance genes.
____ Mechanism for plasmid DNA replication that is unidirectional.
____ Type of autoinducer found in Gram-negative bacteria.
____ ’ subunits of RNA polymerase.
____ Stem loop structure that forms at the end of a mRNA.
____ DNA sequence at which repressors bind to turn off gene expression.
____ The membrane component of a two-component regulatory system.
____ Bacteriophages that can transfer random regions of the host chromosome
____ Antibiotic resistance gene flanked by two insertion sequences.
A. Activator
B. Broad-host range vector
C. Calcium dipicolinate
D. Core enzyme
E. Diaminopimelicacid
F. Generalized transducing phage
G. Glucose-6-phosphate
H. Homologous recombination
I. Homoserine lactone
J. Operator
K. Oxidation
L. Phosphoenolpyruvate
M. 3-Phosphoglycerate
N. Promoter
O. Reduction
P. Rolling circle replication
Q. Selectable marker
R. Sensor
S. Shuttle vector
T. Specialized transducing phage
U. Telomere
V. Terminator
W. Transposon
Short answer. (1 point each)
Deinococcus radiodurans is resistant to very high levels of radiation. What is the reason for this high level of resistance?
Why are plasmids useful as cloning vectors?
Give one reason why endospores are highly resistant to dessication and chemical damage.
Name one signal that triggers sporulation.
In class a growth curve for bacteria in laboratory medium was presented showing a lag phase, exponential phase, stationary
phase and death phase. Why is this unrealistic for microbes growing in nature?
E. coli can use glycerol as an energy source for anaerobic respiration. Electrons from
glycerol enter the electron transport chain at the level of NADH. Either fumarate or
nitrate can function as a terminal electron acceptor. Use of which of these electron
acceptors will result in the most ATP production?
Wollinella succinogenes can use fumarate as a terminal electron acceptor for anaerobic
respiration from glycerol (NADH is the electron donor) or it can use oxygen as a
terminal electron acceptor from succinate. Which of these donor/acceptor
combinations will likely yield the most ATP?
E. coli controls the expression of the genes necessary for the use of specific electron
acceptors based on energy yield. For example, oxgyen is preferred over nitrate and
nitrate is preferred over fumarate. E. coli shows no preference between fumarate and
trimethylamine oxide (TMAO). What would you predict is the approximate Eo’ for
the TMAO(ox)/TMAO(red) couple?
Why does aerobic respiration result in more ATP production than fermentation?
Explain why the transfer of electrons from the flavoprotein of the electron transport chain to the iron-sulfur protein results in
the release of a proton to the outside of the cell but transfer of electrons from NADH to the flavoprotein do not.
What is the advantage to the bacterial cell of using the phosphotransferase system as opposed to using a proton driven sugar
transport system?
What is syntrophy?
How can two genes that belong to a single operon be expressed at different levels?
The Fnr protein of E. coli can function as both a repressor and an activator. Describe the likely location of the DNA binding
site for Fnr when it is functioning as an:
Activator
Repressor
Genes that code for the enzymes involved in the production of the amino acid histidine are likely to be controlled by what type
of repressor?
In the lac operon expression of the enzyme -galactosidase is under the control of the lac repressor (LacI) which binds at the
lac operator (lacO). Complete the table with + if -galactosidase is expressed under the conditions described or – if galactosidase is not expressed under the conditions described.
Mutation
lacI- - doesn’t make LacI
lacIs - LacI can’t bind lactose
Lactose present
Lactose absent
Short Essay Questions. Please answer two of the following three short essay questions (5 points each - 5 bonus points
possible for answering all 3 questions)
The translational machinery of the bacterial cell is the target of numerous antibiotics. Explain why translation is an ideal target
for bacterial inhibitors.
Gene expression can be controlled at the DNA, mRNA and protein levels. Describe how control can occur at each of these
levels.
Describe the flow of electrons from NADH to oxygen in the typical aerobic electron transport chain described in our book.
Indicate which electron transfer reactions result in the release of a proton to the outside of the cell.