BioSc221/325
Exam 3
Name ______________________________
Multiple choice. (1 point each) Choose the one best answer to each of the following questions.
____ 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
____ Natural transformation does not require
A. membrane associated transport proteins
B. linear double stranded DNA
C. holes in the membrane
D. homologous recombination
____ An example of a latent human virus would be
A. herpes simplex
B. influenza
C. ebola
D. T4
____ Genes that are expressed at the same level at all times are said to be
A. constitutive
B. inducible
C. repressible
D. activated
____ A viral protein that associates with the inner surface of the host cytoplasmic membrane and functions in assembly of the
viral envelope is called a(n).
A. matrix protein
B. hemagglutinin
C. pilin
D. replicase
____ Which of the following is not a mechanism for horizontal gene transfer in nature
A. conjugation
B. electroporation
C. transduction
D. transformation
____ 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
____ The RNA-dependent RNA polymerase found in influenza virus which produces a + strand from the - strand influenza
virus genome is called
A. reverse transcriptase
B. helicase
C. neuraminidase
D. replicase
____ 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
____ Viruses typically try to shut down host cell replication and transcription. A major disadvantage to the virus of this
strategy is that ___.
A. host transcription is required for budding.
B. host replication is required for nucleocapsid assembly.
C. blocking host processes may trigger apoptosis.
D. blocking host transcription will block cap “stealing”.
____ 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
____ Genes encoding the enzymes required for synthesis of the amino acid tyrosine are likely to be controlled by what type of
repressor?
A. inducible
B. repressible
C. constitutive
____ Influenza virus inhibits host cell translation and promotes translation of viral transcript by a process known as
A. CAP stealing
B. reverse transcription
C. blocking the shine-dalgarno sequence of host transcripts
D. latency
____ Protein involved in transcriptional termination.
A. core enzyme
B. stem loop
C. rho
D. sigma
____ 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
____ In two-component regulatory systems a signal is relayed to the regulator protein by
A. phosphorylation
B. adenylation
C. autoinducer
D. a peptide
____ Promoter strength is determined by
A. the DNA sequence of the promoter region
B. the number of operators
C. how close the promoter is to the start of transcription
D. the DNA sequence of the ribosome binding site
____ A bacterial strain in which an F plasmid has integrated into the chromosome allowing easy transfer of chromosomal DNA
to a recipient strain is called a(n)
A. conjugative transposon
B. conjugative chromosome
C. R factor
D. HFR
___ Quorum sensing systems use ___ to determine cell density.
A. cell-cell contact
B. autoinducer
C. luminescence
D. phosphotransferase
____ The symptoms of viral infection are primarily due to
A. the body's response to the invasion
B. toxins released by the virus
C. insertion of the viral genome into the host cell
D. all of the above
_____ A repressible operon is important in regulating _____.
A.
B.
C.
D.
Amino acid synthesis
DNA replication
Sugar metabolism
ATP synthesis
_____ Catabolite repressor protein (CRP) binds to DNA when bound to ____ and ____ expression of catabolic operons such as
the lac operon.
A.
B.
C.
D.
E.
Glucose, represses
Glucose, activates
cAMP, represses
cAMP, activates
Lactose, represses
_____ The site of interaction between RNA polymerase and DNA that initiates transcription is called the ___.
A. Pribnow box
B. Shine-Dalgarno sequence
C. Promoter
D. Operator
_____ The genome of a virus is
A. Always DNA
B. Always RNA
C. DNA and RNA
D. Either DNA or RNA
_____ All viruses have
A. capsids
B. envelopes
C. glycoprotein spikes
D. reverse transcriptase
_____ Integrating viral DNA into the genome of a bacterium is termed
A. dormancy
B. lysogeny
C. lytic cycle
D. All of the above
_____ A major factor in viral specificity is
A. DNA specificity
B. attachment
C. RNA specificity
D. the presence of fimbrae
_____ When a virus infects a cell, it supplies ____ for the infection.
A. energy
B. ribosomes
C. enzymes that activate amino acids
D. None of the above
_____ A high error rate in reverse transcriptase causes
A. formation of new variants
B. genetic instability
C. Formation of unstable variants
D. None of the above
_____ A small portion of a 1 liter flask culture of an ampicillin sensitive strain of E. coli (approximately 108 bacteria) is spread
on an agar plate containing ampicillin. After a 24 hour incubation, 50 ampicillin resistant colonies are observed. When did
these ampicillin bacteria arise?
A. in the 1 liter flask, during incubation in the absence of ampicillin
B. on the agar plate, during incubation in the presence of ampicillin
C. E. coli cannot spontaneously become resistant to ampicillin
_____ Based on what you have learned about the elements that control synthesis of the enzymes for tryptophan synthesis, what
effect on enzyme activity would you expect under the following conditions: a mutation in the trpR gene, encoding TrpR the
tryptophan repressor, such that TrpR can bind DNA without the co-repressor
A. constitutive, high-level activity
B. no activity in the absence of tryptophan, high-level activity in the presence of tryptophan
C. high-level activity in the absence of tryptophan, no activity in the presence of tryptophan
D. no activity under any conditions
_____ Based on what you have learned about the elements that control synthesis of the enzymes for tryptophan synthesis, what
effect on enzyme activity would you expect under the following conditions: a mutation in the trpR gene coding for the
tryptophan repressor such that TrpR cannot bind tryptophan
A. constitutive, high-level activity
B. no activity in the absence of tryptophan, high-level activity in the presence of tryptophan
C. high-level activity in the absence of tryptophan, no activity in the presence of tryptophan
D. no activity under any conditions
Short answer. (1 point each)
What is a viral plaque?
What are the four phases involved in viral replication?
If you were designing an antiviral drug what one aspect of the viral infection process might be a good target?
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 relative to the promoter when it is functioning as an:
Activator
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 High if -galactosidase is expressed at high levels under the conditions described
or Low if -galactosidase is expressed at low levels under the conditions described. Assume glucose is not present.
Mutation
lacI- - doesn’t make LacI
Lactose present
Lactose absent
lacIs - LacI can’t bind lactose
Irradiated food is generally considered sterile and at least has a very long shelf life. However, Deinococcus radiodurans was
isolated from irradiated meat. How did it manage to survive this "sterilization" process?
What is the difference between a transposon and an insertion sequence?
What is the difference between a generalized and a specialized transducing phage?
Short Essay Questions. Please answer three of the following four short essay questions (6 points each - 6 bonus points
possible for answering all 4 questions)
Describe the Baltimore System for viral classification. List the six classes of viruses.
Describe the three principle methods for lateral gene transfer.
You are working for a major chemical company that is in the process of developing a new household cleaning product. There
is some concern about the safety of one of the ingredients - a potential carcinogen. Describe in detail how you would go about
testing this ingredient
Draw a growth curve of E. coli growing on glucose and lactose showing optical density vs. time. Describe what is happening
and why?