WorksheetsGenomics - L8
Total questions: 65
Worksheet time: 33mins
Name
Class
Date
1.
What is an operon?
a)
A eukaryotic gene cluster with multiple start sites
b)
A single bacterial gene controlled by its own promoter
c)
A set of adjacent bacterial genes transcribed together under a single promoter
d)
A protein complex that blocks transcription
2.
What happens in positive regulation of the lac operon?
a)
An activator protein responds to low glucose by enhancing transcription
b)
A repressor protein binds directly to the RNA polymerase
c)
The operon is activated only in high glucose conditions
d)
A terminator sequence is formed in response to lactose
3.
How is the lac operon negatively regulated?
a)
The repressor protein binds to the operator to block transcription
b)
RNA polymerase is inactivated by glucose
c)
The CRP protein represses transcription
d)
The promoter sequence is removed
4.
What is the regulatory mechanism of the ara operon?
a)
AraC represses the operon in the presence of glucose
b)
AraC acts only as an activator
c)
AraC functions as both a repressor and an activator depending on arabinose
d)
The ara operon is regulated by the Lac repressor
5.
How is the trp operon regulated?
a)
Only through CRP-cAMP activation
b)
By a repressor and transcriptional attenuation based on tryptophan levels
c)
Through the presence of glucose and lactose
d)
By silencing mRNA using small RNAs
6.
A set of adjacent bacterial genes that are transcribed together are known as a…
a)
cluster
b)
polyprotein
c)
operon
d)
regulator
7.
What is the idea behind operons?
a)
Genes are separated for individual expression
b)
Each gene uses its own promoter and repressor
c)
Functionally related genes are grouped for coordinated regulation
d)
Operons only work in eukaryotes
8.
Which of these is not a classic example of an operon?
a)
lac
b)
ara
c)
trp
d)
actin
9.
Operons are sets of genes that…
a)
share the same repressor binding site
b)
have the same ribosome
c)
have the same promoter
d)
code for identical proteins
10.
Lac operon contains 3 genes coding for E. coli proteins to use lactose. Which of these is NOT one of those proteins?
a)
Lac permease
b)
Beta-galactosidase
c)
Galactoside transacetylase
d)
Hexokinase
11.
What genes are in the lac operon?
a)
LacX, LacY, LacZ
b)
LacZ, LacY, LacA
c)
LacA, LacI, LacP
d)
LacM, LacQ, LacA
12.
What does polycistronic message mean?
a)
RNA that codes for one protein
b)
RNA with multiple promoters
c)
RNA that encodes several proteins from one mRNA
d)
RNA without a ribosome binding site
13.
Which of these is NOT true about the lac operon?
a)
All three genes are transcribed into one mRNA
b)
Each gene has its own ribosome binding site
c)
Each gene can be translated independently
d)
Each gene has its own promoter
14.
Which gene produces the Lac repressor?
a)
LacZ
b)
LacI
c)
LacY
d)
LacA
15.
How does the lac repressor work?
a)
Binds to promoter and enhances transcription
b)
Binds to ribosome binding site
c)
Binds to the operator and blocks RNA polymerase
d)
Destroys lactose
16.
The lac repressor is an…
a)
Enzyme
b)
Allosteric protein
c)
Activator
d)
mRNA transcript
17.
What is the inducer of the lac repressor?
a)
Glucose
b)
Lactose
c)
Allolactose
d)
Galactose
18.
What is a synthetic analogue of allolactose?
a)
CRP
b)
IPTG
c)
SDS
d)
ADP
19.
What is the structure of the Lac repressor?
a)
Monomer
b)
Dimer
c)
Trimer
d)
Tetramer
20.
What is catabolite repression in lac expression?
a)
Activation by lactose only
b)
Repression by glucose breakdown products
c)
Expression due to allolactose
d)
Activation by IPTG
21.
How does the cell sense a drop in glucose level?
a)
It activates ribosomes
b)
It increases IPTG
c)
It increases cyclic-AMP levels
d)
It expresses the lacI gene
22.
When glucose levels are low, the concentration of cAMP is…
a)
High
b)
Low
c)
Constant
d)
Absent
23.
Positive control of the lac operon has two parts:
a)
cAMP and allolactose
b)
RNA polymerase and repressor
c)
cAMP and CAP/CRP
d)
LacA and LacY
24.
CRP-cAMP complex binds to the ______ which ______
a)
operator, prevents transcription
b)
promoter, induces transcription
c)
lacZ gene, increases translation
d)
terminator, stops RNA polymerase
25.
Binding sites for CRP in lac, gal, and ara operons all contain the sequence…
a)
TGTGA
b)
AACCG
c)
CTAGG
d)
TTGAC
26.
CRP-cAMP activated operons…
a)
Have strong promoters requiring no regulation
b)
Are unaffected by glucose levels
c)
Have weak promoters needing CRP-cAMP for activation
d)
Use riboswitches
27.
How does CRP-cAMP induce stronger binding?
a)
It binds to LacZ
b)
It removes repressors
c)
It interacts with the alpha-CTD of RNA polymerase
d)
It methylates DNA
28.
What does the ara operon code for?
a)
Enzymes that degrade tryptophan
b)
Proteins for glucose uptake
c)
Enzymes to metabolize arabinose
d)
Structural proteins for pili
29.
What are the two ara operators?
a)
araX and araZ
b)
araA and araB
c)
araO1 and araO2
d)
araD and araE
30.
What is unique about the ara operon repression loop?
a)
It involves no DNA looping
b)
It controls a gene 10 bp downstream
c)
It loops DNA between sites 210 bp apart to block transcription
d)
It uses riboswitches to stop translation
31.
AraC is…
a)
An activator only
b)
A repressor only
c)
Both a positive and negative regulator
d)
A sigma factor
32.
What does arabinose do in the ara operon?
a)
Binds to RNA polymerase
b)
Degrades the repressor
c)
Binds to AraC and breaks the DNA loop
d)
Inhibits translation
33.
CRP-cAMP assists ara operon expression by…
a)
Blocking arabinose uptake
b)
Binding to araO2
c)
Breaking the DNA loop and helping AraC bind araI
d)
Inhibiting RNA polymerase
34.
What is the role of AraC in absence of arabinose?
a)
Binds upstream to enhance transcription
b)
Forms a DNA loop by binding araO2 and araI1
c)
Binds to operator and degrades mRNA
d)
Becomes inactive
35.
How is AraC activated?
a)
By glucose binding
b)
By arabinose binding
c)
By ribosome stalling
d)
By IPTG binding
36.
AraC also regulates…
a)
Translation of arabinose
b)
Its own expression
c)
The trp operon
d)
CRP gene expression
37.
The trp operon codes for…
a)
Enzymes that break down tryptophan
b)
Enzymes that synthesize tryptophan
c)
Structural ribosome proteins
d)
Lactose-metabolizing enzymes
38.
What two methods are used to regulate the trp operon?
a)
Lac repressor and cAMP
b)
AraC and CRP
c)
Trp repressor and attenuation
d)
Riboswitch and methylation
39.
Where is the trp operator located?
a)
Within the trpA gene
b)
Inside the terminator region
c)
Within the trp promoter
d)
On a separate plasmid
40.
Without tryptophan, the inactive protein is known as…
a)
Prepressor
b)
Aporepressor
c)
Corepressor
d)
Terminator
41.
The trp repressor is a combination of…
a)
CRP and glucose
b)
Aporepressor and tryptophan
c)
Sigma factor and RNA polymerase
d)
cAMP and lactose
42.
What is attenuation in the trp operon?
a)
A mechanism of RNA degradation
b)
A feedback loop involving allolactose
c)
Transcriptional control based on ribosome position and mRNA structure
d)
Inhibition of translation initiation
43.
The trp repressor causes a ____ fold decrease in expression, compared to attenuation which gives a ____ fold control.
a)
10, 70
b)
2, 200
c)
70, 10
d)
100, 1
44.
Repression of the trp operon relies on…
a)
Glucose concentration
b)
Aporepressor binding to trpE
c)
Two consecutive Trp codons in the leader peptide
d)
A CRP-dependent activator
45.
When tryptophan levels are low…
a)
RNA polymerase stalls at operator
b)
The hairpin loop forms at the attenuator
c)
The ribosome stalls, preventing formation of the terminator hairpin
d)
The repressor binds more tightly
46.
Which part of the trp mRNA is involved in attenuation?
a)
Promoter
b)
Shine-Dalgarno sequence
c)
Leader region with multiple hairpin options
d)
Coding region of trpE
47.
What is formed during attenuation that halts transcription?
a)
Terminator protein
b)
Terminator hairpin loop followed by a poly-U sequence
c)
Ribosome binding complex
d)
tRNA-tryptophan hybrid
48.
What causes the terminator loop to form in high tryptophan conditions?
a)
Sigma factor displacement
b)
Ribosome stalling at Trp codons
c)
Ribosome moves quickly, allowing region 3 and 4 to pair
d)
AraC repression
49.
Which regulatory mechanism allows rapid adjustment of tryptophan biosynthesis?
a)
Riboswitch control
b)
DNA methylation
c)
Attenuation via translation-transcription coupling
d)
Plasmid loss
50.
Why is attenuation only possible in prokaryotes?
a)
Eukaryotes lack repressors
b)
Eukaryotic genes are monocistronic
c)
Transcription and translation are not coupled in eukaryotes
d)
Only bacteria make tryptophan
51.
What type of control is attenuation classified as?
a)
Translational
b)
Post-translational
c)
Transcriptional fine-tuning
d)
Epigenetic
52.
Which of the following is true about lac operon and trp operon regulation?
a)
Both use the same repressor protein
b)
Both are activated by CRP
c)
Lac is inducible; trp is repressible
d)
Trp uses allolactose; lac uses tryptophan
53.
What kind of regulation does the trp operon primarily use?
a)
Induction by sugar
b)
Repression and attenuation
c)
Activation by CRP
d)
Ribosome skipping
54.
Which is NOT a shared feature between lac, ara, and trp operons?
a)
Presence of promoter regions
b)
Polycistronic mRNA
c)
Regulation by operator binding
d)
Use of sigma factor 70
55.
What is the main function of allolactose in lac operon regulation?
a)
Acts as a repressor
b)
Enhances translation
c)
Induces transcription by inactivating the Lac repressor
d)
Binds CRP to activate the promoter
56.
What happens if both lactose and glucose are present?
a)
Lac operon is strongly activated
b)
Lac operon is repressed by catabolite repression
c)
Trp operon activates instead
d)
Ara operon is activated
57.
Which operon uses DNA looping as part of its regulation?
a)
Lac only
b)
Trp only
c)
Ara only
d)
Both lac and ara
58.
Which molecule is essential for positive regulation in both lac and ara operons?
a)
IPTG
b)
Trp
c)
cAMP-CRP complex
d)
DNA polymerase
59.
What effect does arabinose have on AraC?
a)
Causes DNA looping
b)
Inhibits transcription
c)
Converts AraC from a repressor to an activator
d)
Destroys CRP
60.
What role does the leader peptide play in the trp operon?
a)
Prevents translation
b)
Promotes translation of lac genes
c)
Determines whether transcription will terminate or continue
d)
Binds the repressor protein
61.
What is an operon?
a)
A single eukaryotic gene with no promoter
b)
A viral regulatory region
c)
Adjacent bacterial genes transcribed together
d)
A segment of RNA spliced out during translation
62.
What role does the Lac repressor play in the lac operon?
a)
Enhances gene expression
b)
Prevents RNA polymerase binding by binding the operator
c)
Synthesizes lactose
d)
Binds to glucose
63.
Under what condition does CRP-cAMP activate the lac operon?
a)
In high glucose conditions
b)
In presence of tryptophan
c)
In absence of glucose
d)
When allolactose is absent
64.
How does AraC repress the ara operon?
a)
It degrades arabinose
b)
It blocks translation at the ribosome
c)
It loops out DNA between two sites
d)
It removes the CRP complex
65.
What does the trp attenuator do in high tryptophan conditions?
a)
Initiates RNA synthesis
b)
Promotes ribosome skipping
c)
Causes premature termination of transcription
d)
Stimulates trp operon repressor production
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