Chapter 36 RNA Synthesis and Regulation in Prokaryotes
Matching Questions
Use the following to answer questions 1–10:
Choose the correct answer from the list below. Not all of the answers will be used.
a) divalent cation
b) primer
c) stem loop
d) operon
e) consensus
f) amanitin
g) transcription
h) translation
i) repressor
j) transcription bubble
k) catabolite repression
l) promoters
1.
______________ A group of genes that are closely related and are produced as a single mRNA.
2.
RNA synthesis (tRNA, mRNA, and rRNA) is called ______________.
Ans:
g
Section: 36.1
3.
______________ is a required cofactor for RNA polymerase.
Ans:
Section: 36.1
4.
DNA sequences that direct RNA polymerase to the initiation site are called ______________.
Ans:
Section: 36.2
5.
Unlike DNA synthesis, RNA synthesis does not require a(n) ______________.
Ans:
b
Section: 36.1
6.
The region of RNA synthesis containing the DNA, RNA, and enzymes is called the
______________.
Ans:
Section: 36.2
7.
______________ Sequences deduced from the analysis of many related DNA sequences.
Ans:
Section: 36.1
Ans:
d
Section: 36.3
Chapter 36 RNA Synthesis and Regulation in Prokaryotes
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8.
The expression of galactosidase requires the induction of an operon by removal of a(n)
______________.
9.
The RNA structure that often signals termination of transcription is the ______________.
Ans:
Section: 36.2
10.
An increase in cellular metabolism that inhibits expression of the genes for that metabolism is a
process known as ______________.
Ans:
k
Section: 36.3
Fill–in-the-Blank Questions
11.
RNA polymerases read the template strand in the _____ direction.
Ans: 3 → 5 Section: 36.1
12.
Promoter sites in E. coli are located _____ and _____nucleotides upstream of the start site.
Ans: −10 and −35 Section: 36.1
13.
The _____ sequence is determined by an alignment of DNA base sequences used to deduce a
recurring pattern or motif.
Ans: consensus Section: 36.1
14.
The coding strand has the _____ sequence as the RNA transcript (except that it has T instead of
U).
Ans: same Section: 36.1
15.
The first step of transcription depends on the _____ subunit.
Ans: σ Section: 36.1
16.
The RNA polymerase can unwind approximately _____ bases, or about 1.6 turns of B-DNA.
Ans: 17 Section: 36.2
17.
The rate of RNA synthesis in E. coli is approximately _____ nucleotides per second.
Ans: 50 Section: 36.2
18.
The Rho protein terminates transcription by acting as a _____.
Ans: helicase Section: 36.2
19.
Many antibiotics, such as rifampicin, function by blocking _____.
Ans: RNA synthesis Section: 36.2
20.
Adding lactose to E. coli culture results in _____ of expression of the lac operon.
Ans: induction Section: 36.3
Ans:
Chapter 36 RNA Synthesis and Regulation in Prokaryotes
3
Multiple-Choice Questions
21.
Functions of RNA polymerase include
A)
searching for promoter sites.
B)
unwinding short stretches of DNA.
C)
detecting termination signals.
D)
A and C
E)
A, B, and C
22.
RNA polymerase requires which of the following for initiation?
A)
DNA primer
B)
RNA primer
C)
supercoiled DNA
D)
nicked DNA
E)
None of the above.
Ans: E Section: 36.2
23.
The structure of DNA must be in which complex for transcription to occur?
A)
the closed promoter complex
B)
the biphasic promoter complex
C)
the open promoter complex
D)
All of the above.
E)
None of the above.
Ans: C Section: 36.2
24.
The major RNA types include
A)
messenger RNA
B)
template RNA
C)
ribase RNA
D)
All of the above.
E)
None of the above.
Ans: A Section: 36.1
25.
The Pribnow box
A)
is found +10 base pairs from the start site of an operon.
B)
is found −10 base pairs from the end site.
C)
is the site where promotors bind.
D)
serves to regulate translation.
E)
None of the above.
Ans: C Section: 36.2
26.
The protein that binds DNA sequences and helps RNA polymerases initiate transcription is
A)
B)
C)
D)
.
E)
σ.
Ans: E Section: 36.2
Ans: E Section: Introduction
Chapter 36 RNA Synthesis and Regulation in Prokaryotes
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27.
In transcription, the 3-hydroxyl group
A)
attacks the -phosphorous group on an incoming nucleotide.
B)
binds to a Mg2+ in the active site.
C)
binds to the 5 ribose.
D)
attacks the 5 hydrogen of the incoming nucleotide.
E)
None of the above.
28.
Which subunit of E. coli RNA polymerase binds DNA and takes part in catalysis?
A)
B)
C)
D)
E)
σ
Ans: D Section: 36.1
29.
Structural diversity of tRNA molecules is caused by
A)
folding patterns.
B)
methylation of the ribose.
C)
poly(A) tailing.
D)
All of the above.
E)
None of the above.
Ans: B Section: 36.2
30.
In E. coli, what other protein(s) is(are) synthesized when –galactosidase is synthesized?
A)
σ70 of RNA polymerase
B)
RNA helicase
C)
ribonuclease III
D)
galactoside permease
E)
All of the above.
Ans: D Section: 36.3
31.
An RNA mutation improves the error rate slightly at the expense of a slightly slow transcription
speed. Is this a significant improvement?
A)
No, because transcription takes place at a rate nearly 50 times that needed by most cells.
B)
No, because an error in mRNA affects only one molecule and the error does not become
part of the permanent genome,
C)
Yes, because fewer errors in transcription give bacteria, who turnover rapidly, a survival
advantage.
D)
Yes, because bacteria turnover rapidly, and so protein synthesis runs a maximum
capacity.
E)
Yes, because the transcription bubble is stable only at slow transcription rates.
Ans: B Section: 36.2
Ans: A Section: 36.2
Chapter 36 RNA Synthesis and Regulation in Prokaryotes
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32.
What would happen if regions of DNA encoding the CAP were deleted?
A)
Bacterial growth would be inhibited because β-galctosidase would remain low even when
glucose levels are low.
B)
This condition would effectively drive lipid production due to excess glucose
metabolism.
C)
On a molecular level, the lac repressor would stay bound to the operon preventing
transcription.
D)
This would activate the catabolite repression mechanism in the presence of glucose.
E)
The bacteria would switch to glycogen metabolism.
33.
If you were to target a mutation in RNA polymerase to inhibit bacterial growth, which subunit
would you target and why?
A)
σ-subunit because it binds to DNA.
B)
α-subunit because it takes part in promoter recognition.
C)
α-subunit because it binds to DNA.
D)
β-subunit because it is required to restore denatured polymerase.
E)
β-subunit because it takes part in all stages of catalysis.
Ans: E Section: 36.2
34.
Would it be possible to predict the complete sequence of a tRNA molecule knowing the DNA
sequence that encodes for it?
A)
Yes, tRNA is transcribed in the same process as mRNA.
B)
Yes, tRNA forms short sequences of Watson-Crick base pairing.
C)
Yes, primer sequences are regulated the same for all types of RNA.
D)
No, tRNA is modified enzymatically after transcription.
E)
No, tRNA is not translated, and so sequence data is unavailable.
Ans: D Section: 36.2
35.
What parallels are there between the lac operon and a gene for an allosteric enzyme?
A)
Both respond to cAMP cascades.
B)
Both contain both regulatory regions and structural genes.
C)
Transcription of both requires the formation of a hairpin loop.
D)
Both are sensitive to actinomycin D inhibition.
E)
Transcription of the regulator gene requires binding of the inducer to the promoter.
Ans: B Section: 36.3
Short-Answer Questions
36.
Name the three stages of RNA synthesis.
Ans:
The three stages of RNA synthesis are initiation, elongation, and termination.
Section: 36.1
37.
How do promoters differ in efficiency?
Section: 36.2
Ans: A Section: 36.3
Chapter 36 RNA Synthesis and Regulation in Prokaryotes
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38.
What is the significance of the subunit?
39.
How does RNA polymerase find the proper binding site?
Ans:
The RNA polymerase binds to the DNA and slides along it until the proper site is found.
Section: 36.1
40.
What is the theory about how palindromic RNA polymerase transcription termination signals
function?
the palindromic sequence, and the DNA template separates from the nascent RNA at this
point.
Section: 36.2
41.
What is a common feature of both protein-dependent and protein-independent termination
signals in transcription?
Ans:
The signals that mediate termination events appear to function in the newly synthesized
RNA and not in the template DNA.
Section: 36.2
42.
How does the antibiotic rifamycin function mechanistically?
phosphodiester bonds.
Section: 36.2
43.
A σ subunit that is mutated such that the protein binds tightly to DNA with a 10-times-higher
affinity than wild-type sequences will likely have what effect?
RNA at the upstream Pribnow elements. If the protein were to bind tightly, then the
polymerase would not be able to bind the DNA to initiate transcription.
Section: 36.2
44.
Describe how RNA is modified.
Ans:
Both tRNA and rRNA are modified chemically. Some RNAs are extended, others are
cleaved into smaller mature RNAs, and in still others, nucleotides may be methylated.
Section: 36.2
45.
How does the addition of lactose to E. coli induce the expression of proteins important for
lactose metabolism?
repressor protein, causing the protein to release from the upstream elements of the lac
operon.
Section: 36.3
interaction by decreasing the binding affinity of nonspecific interactions.
Section: 36.3
Chapter 36 RNA Synthesis and Regulation in Prokaryotes
7
46.
A mutation in the 3 end of mRNA leads to an increase in AT-rich regions. What is the likely
outcome of this change?
47.
What are the DNA components of a regulatory system?
a regulatory system The regulator gene encodes for the repressor protein that binds to the
operator site.
Section: 36.3
48.
How is the expression of the lac operon inhibited by the lac repressor?
transcription of the structural genes.
Section: 36.3
49.
What is the social interaction known as quorum sensing and how does it change gene
expression?
complexes with a regulatory protein. The inducer–regulatory protein complex acts to alter
gene transcription.
Section: 36.3
50.
What are riboswitches and how do they control gene expression?
capable of directly binding small molecules. The mRNA-molecule complex then affects
the biosynthesis of related molecules.
Section: 36.3
Ans:
The termination signal includes a stem-loop structure formed by GC-rich repeats. Loss of
the structure will create indiscriminate stop sites for the mRNA product.
Section: 36.2