Question 1

Which of the following best describes the difference between structural genes and regulatory genes?

Accepted Answer

Structural genes encode proteins; regulatory genes control the transcription of structural genes.

Question 2

A negative inducible operon is characterized by which of the following?

Accepted Answer

The repressor is active and binds to the operator, preventing transcription until an inducer inactivates it.

Question 3

In the lac operon, what is the role of allolactose?

Accepted Answer

It acts as an inducer by binding to the repressor and preventing it from binding to the operator.

Question 4

Which of the following statements about catabolite repression in the lac operon is correct?

Accepted Answer

Low glucose increases cAMP, which binds to CAP, allowing the CAP-cAMP complex to activate transcription of the lac operon.

Question 5

In a negative repressible operon, the regulator protein is synthesized as:

Accepted Answer

an inactive repressor

Question 6

For a(n) repressible operon, transcription normally takes place, and it is turned off by a(n):

Accepted Answer

repressor

Question 7

In the presence of allolactose, the lac repressor:

Accepted Answer

cannot bind to the operator

Question 8

A mutation in the operator site of the lac operon (lacOc) results in which of the following?

Accepted Answer

Constitutive expression of the structural genes, regardless of the presence of lactose

Question 9

Which of the following best describes a cis-acting mutation?

Accepted Answer

It affects only genes located on the same DNA molecule, such as mutations in the operator or promoter.

Question 10

A partial diploid E. coli strain has the genotype lacI+ lacO+ lacZ- / lacI- lacOc lacZ+. Which statement is correct regarding β-galactosidase expression?

Accepted Answer

β-galactosidase will be produced constitutively.

Question 11

Which of the following is NOT a result of low glucose levels in E. coli?

Accepted Answer

CAP-cAMP loses its affinity to DNA

Question 12

In the trp operon, what happens to the trp repressor in the absence of tryptophan?

Accepted Answer

It cannot bind to the operator and transcription takes place.

Question 13

Which of the following is a key feature of eukaryotic gene regulation that distinguishes it from prokaryotic gene regulation?

Accepted Answer

The use of enhancers and silencers that can be located far from the gene they regulate.

Question 14

Which of the following mechanisms is an example of epigenetic gene regulation?

Accepted Answer

DNA methylation of cytosine residues to form 5-methylcytosine

Question 15

A positive inducible operon is characterized by which of the following?

Accepted Answer

An activator protein must be activated by an inducer to stimulate transcription.

Question 16

Which of the following best explains why the repression of the lac operon never completely shuts down transcription?

Accepted Answer

There is always a low level of transcription to allow for rapid response to lactose availability.

Question 17

Which of the following is a real-world example of coordinated gene regulation in eukaryotes?

Accepted Answer

A group of genes involved in the immune response are activated simultaneously by the same transcription factor during infection.

Question 18

Which of the following equations correctly represents the relationship between DNA, mRNA, and protein in gene expression?

Accepted Answer

$$DNA \xrightarrow{transcription} mRNA \xrightarrow{translation} Protein$$

Question 19

A mutation in the lacI gene that produces a super-repressor (lacIs) will have what effect on the lac operon?

Accepted Answer

The operon will be permanently repressed, regardless of the presence of lactose.

Gene Expression Control: Bacterial and Eukaryotic Regulation

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