Bacterial Gene Regulation

Concept: Bacterial Regulation of Gene Expression

10m

Concept: The lac Operon

10m

Concept: The trp Operon

7m

Bacterial Gene Regulation Additional Practice Problems

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.

Watch Solution

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.

Watch Solution

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.

Watch Solution

Which of the following is not a component of the bacterial Trp operon?

A. promoter

B. inducer

C. TrpD gene

D. operator

Watch Solution

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.

Watch Solution

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

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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

Watch Solution

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.

Watch Solution

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.

Watch Solution

Which region(s) of the lac operon affect the binding of RNA polymerase? Check all that apply.

A. CAP binding site

B. lacO

C. lacZ

D. lacY

E. lacA

Watch Solution

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.

Watch Solution

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.

Watch Solution

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.

Watch Solution

What are the typical components of an operon, and what roles do they play in inducing enzyme synthesis?

Watch Solution

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

Watch Solution

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

Watch Solution

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

Watch Solution

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

Watch Solution

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

Watch Solution

 Explain why the lac genes are not transcribed in the presence of glucose. 

Watch Solution

Explain the role of allolactose in regulation of the lac genes.

Watch Solution

What is the effect of over-expression of Bcl-2?

A. promote cancer development

B. prevent cancer development

Watch Solution

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

Watch Solution

 Is the absence of the lac repressor sufficient for initiation of transcription of the lac operon?

Watch Solution

Can attenuation take place in eukaryotes?

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 What is an operon? How do operons function in bacteria to control gene transcription?

Watch Solution

How is quorum sensing linked to the development of antibiotic resistance?

Watch Solution

What are the three different types of horizontal gene transfer? Name, describe and compare them.

Watch Solution

Describe mycolic acids. Why is it worth it to Mycobacteria to spend the time it takes to make the chemicals?

Watch Solution

Compare and contrast Mycobacteria and Mycoplasma regarding 1) structure, 2) favored location, 3) virulence factors.

Watch Solution

During infection, what part of the virus enters a bacterium?

Watch Solution

Describe the two ways in which the amino acid tryptophan regulates expression of the trp operon in E. coli.

Watch Solution

Why is topoisomerase activity necessary for transcription?

Watch Solution

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? 


Watch Solution

Bacteria divide using _________. 


Watch Solution

Select the terms on the left to the appropriate blanks on the right to complete the sentences. 

Watch Solution

List two bacterial cell structures that could also be described as virulence factors and explain.

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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?

Watch Solution

How do you distinguish bacterial cells that carry a vector from those that do not?


Watch Solution

In the absence of glucose, when lactose is present it combines with the repressor, allowing RNA polymerase to carry on transcription.

a. True

b. False

Watch Solution

Operons are found in eukaryotes but not in prokaryotes.

a. True

b. False

Watch Solution

In the presence of tryptophan, transcription of the trp operon is on.

a. True

b. False

Watch Solution

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.

 

Watch Solution

The trp operon consists of ________ genes that encode tryptophan biosynthesis enzymes.

a. one

b. two

c. three

d. four

e. five

 

Watch Solution

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

Watch Solution

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

Watch Solution

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

e. Lactose

Watch Solution

In the Lac operon, the attachment site for RNA polymerase is: 

a. The operator

b. The promoter

c. The repressor

 

Watch Solution

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

Watch Solution