Concept: Bacterial Regulation of Gene Expression10m
Concept: The lac Operon10m
Concept: The trp Operon7m
Under conditions of high glucose and high lactose concentration, what will happen to the levels of β-galactosidase?
A. Essentially no β-galactosidase will be produced.
B. It depends on what other sugars are present in the growth medium.
C. High levels of β-galactosidase will be produced.
D. Moderate levels of β-galactosidase will be produced.
How does the presence of glucose in an E. coli's environment affect the transcription of the lac operon? Select all that apply.
A. Increased glucose levels increase the level of cAMP, leading to more frequent transcription.
B. Glucose will bind the repressor protein so that it can no longer cover the operator.
C. Glucose will bind CAP, helping RNA polymerase bind more tightly to the operon's promoter.
D. Increased glucose levels decrease the level of cAMP, leading to less frequent transcription.
If the lac repressor were altered so it could not release lactose once lactose was bound to it then you would predict that:
A. The repressor could not bind to DNA.
B. The repressor would always be bound to DNA.
C. The repressor could bind to DNA only when cells were grown with glucose.
D. The repressor could bind to DNA only when cells were grown without glucose.
Which of the following is not a component of the bacterial Trp operon?
C. TrpD gene
Which is incorrect about inducible operons?
A. They have genes turned off by the buildup of end product.
B. They are often for use in catabolic pathways.
C. They are normally turned off.
D. They are turned on by the substrate of the enzyme.
E. They include the lac operon.
Repressible operons require that ____ binds to the repressor protein before it can bind to the operator.
A. the product
B. a cofactor
C. a coenzyme
D. the substrate
E. the reactant
Gene expression from the lac operon can be controlled in many ways, including a robust negative regulation strategy. Select mutations that would reduce the effectiveness of this negative regulation and increase lac operon activity.
A. mutation that deletes the lacI gene
B. mutation of the -10 promoter sequence to more closely resemble the E.coli consensus sequence
C. mutation that increases the affinity of the operator regions for lactose repressor
D. mutation that reduces the affinity of the lactose repressor for lactose
E. mutation of the -10 promoter sequence to be less similar to the E. coli consensus sequence
A deletion of the operator sequence in the lac operon would:
A. never express lac structural genes.
B. not bind the repressor and constitutively express the lac structural genes.
C. not bind the cCAMP-CAP complex.
D. not bind to the repressor and never express lac structural genes.
In an E. coli mutant carrying a deletion of the trp operator sequence..
A. transcription of the trp operon will proceed in the presence or absence of tryptophan.
B. the trp repressor will always be active.
C. no translation of trp operon genes will occur in the presence or absence of tryptophan.
D. no transcription of the trp operon will occur in the presence or absence of tryptophan.
Which region(s) of the lac operon affect the binding of RNA polymerase? Check all that apply.
A. CAP binding site
In the absence of tryptophan,
A. the inducer cannot bind trpO, so operon gene transcription occurs.
B. the active repressor cannot bind trpO, so operon gene transcription is attenuated.
C. the inactive repressor cannot bind trpO, so operon gene transcription occurs.
D. the repressor binds the corepressor, and operon gene transcription occurs.
E. the active repressor binds trpO, so operon gene transcription is repressed.
Which of the following is true about operons?
A. Operons afford the organism the opportunity to simultaneously regulate transcription of multiple genes, whose products are active in the same process.
B. Promoters and repressors as parts of operons serve as information integrating units, thereby affording more flexible response to the environmental changes.
C. Operons provide redundancy in proofreading the most essential parts of genetic code, thereby reducing the susceptibility of the organisms to lethal mutations.
D. Operons, significantly increase the rate of DNA replication, thereby ensuring the required rate of bacteria reproduction.
What is the likely state of the lac operon in conditions in which glucose is very low and lactose is plentiful?
A. The CAP protein is bound to the CAP site, and allolactose is bound to the repressor.
B. The polycistronic mRNAs are not translated.
C. Transcription of the LacZ gene is high but transcription of the LazY gene is low.
D. The CAP protein is bound to the CAP site, and the repressor is bound to the operator.
What are the typical components of an operon, and what roles do they play in inducing enzyme synthesis?
Several examples ofantisense RNA regulating translation in bacterial cells have been discovered, Molecular geneticists have also used antisense RNA to artificially control transcription in both bacterial and eukaryotic genes.
If you wanted to inhibit the transcription of a bacterial gene with antisense RNA, what sequence might the antisense RNA contain?
A. a sequence that is identical to the gene that codes for RNA polymerase
B. a sequence complementary to the structural gene
C. a sequence complementary to the promoter of the operon
D. a sequence complementary to the 3' UTR
E. a sequence complementary to the 5' UTR
When arabinose is present and glucose is absent,
A. the ara operon will be turned on by positive control
B. the ara operon will be turned on by negative control
C. the ara operon will be turned off by positive control
D. the ara operon will be turned off by negative control
E. the ara operon will first turn on then turn off
When the lac operon is turned on, it is said to be under:
A. Regulatory control
B. Negative control
C. Combinatorial control
D. Negative control
The arginine operon is usually in the _____ position and is _____ by the product.
A. off; repressed
B. on; repressed
C. off; induced
D. on; induced
The lac operon is usually in the _____ position and is activated by a/an _____ molecule.
A. off, repressor
B. on, repressor
C. off, inducer
D. on, inducer
Explain why the lac genes are not transcribed in the presence of glucose.
Explain the role of allolactose in regulation of the lac genes.
What is the effect of over-expression of Bcl-2?
A. promote cancer development
B. prevent cancer development
What is the function of the product of the galR gene in regulation of the gal operon?
A. A positive regulator of the gal operon
B. A negative regulator of the gal operon
C. Both a positive and a negative regulator of the gal operon
D. Sigma factor required expression the gal operon
Is the absence of the lac repressor sufficient for initiation of transcription of the lac operon?
Can attenuation take place in eukaryotes?
What is an operon? How do operons function in bacteria to control gene transcription?
How is quorum sensing linked to the development of antibiotic resistance?
What are the three different types of horizontal gene transfer? Name, describe and compare them.
Describe mycolic acids. Why is it worth it to Mycobacteria to spend the time it takes to make the chemicals?
Compare and contrast Mycobacteria and Mycoplasma regarding 1) structure, 2) favored location, 3) virulence factors.
During infection, what part of the virus enters a bacterium?
Describe the two ways in which the amino acid tryptophan regulates expression of the trp operon in E. coli.
Why is topoisomerase activity necessary for transcription?
1. What would happen to transcription of the lac operon in an E. coli cell without a functional CAP protein? What would happen in a cell without a functional lac repressor?
Bacteria divide using _________.
Select the terms on the left to the appropriate blanks on the right to complete the sentences.
List two bacterial cell structures that could also be described as virulence factors and explain.
What is meant by a repressible operon? In the case of the trp operon, how is repression exerted? If someone asked you to genetically engineer a strain of E. coli to produce large amounts of tryptophan, what would be the easiest way to do that?
How do you distinguish bacterial cells that carry a vector from those that do not?
In the absence of glucose, when lactose is present it combines with the repressor, allowing RNA polymerase to carry on transcription.
Operons are found in eukaryotes but not in prokaryotes.
In the presence of tryptophan, transcription of the trp operon is on.
In the absence of tryptophan, the trp repressor is:
a. active and can bind to the operator.
b. active and cannot bind to the operator.
c. inactive and can bind to the operator.
d. inactive and cannot bind to the operator.
The trp operon consists of ________ genes that encode tryptophan biosynthesis enzymes.
If E. coli bacteria are grown in the absence of lactose:
a. The repressor will not bind the operator allowing transcription of the lac operon genes
b. The repressor will bind the operator allowing transcription of the lac operon genes
c. The repressor will not bind the operator preventing transcription of the lac operon genes
d. The repressor will bind the operator preventing transcription of the lac operon gene
If E. coli bacteria are grown in the presence of lactose:
a. The repressor will bind the operator allowing transcription of the lac operon genes
b. The repressor will not bind the operator preventing transcription of the lac operon genes
c. The repressor will not bind the operator allowing transcription of the lac operon genes
d. The repressor will bind the operator preventing transcription of the lac operon genes
In the Lac operon, the protein that binds to the operator to prevent transcription is:
a. The repressor
b. RNA polymerase
c. DNA polymerase
d. The promoter
In the Lac operon, the attachment site for RNA polymerase is:
a. The operator
b. The promoter
c. The repressor
A group of prokaryotic genes and other segments of DNA that are controlled together is:
a. A proteome
b. A chromosome
c. A ribosome
d. A replication fork
e. An operon