$$\text{Lactose} + \text{H}_2\text{O} \rightarrow \text{Galactose} + \text{Glucose}$$

Question 1

Which of the following best describes the function of the promoter region in prokaryotic gene regulation?

Accepted Answer

It is the DNA sequence where RNA polymerase binds to initiate transcription.

Question 2

In the lac operon, what is the effect of a mutation in the lacZ gene?

Accepted Answer

The cell cannot convert lactose into galactose and glucose.

Question 3

Which equation correctly represents the reaction catalyzed by β-galactosidase?

Accepted Answer

$$	ext{Lactose} + 	ext{H}_2	ext{O} ightarrow 	ext{Galactose} + 	ext{Glucose}$$

Question 4

What is the role of the operator sequence in the lac operon?

Accepted Answer

It is a cis-acting element that must be adjacent to the promoter to function.

Question 5

Which scenario best illustrates negative control of gene expression in bacteria?

Accepted Answer

Transcription occurs unless it is shut off by a repressor protein binding to the operator.

Question 6

A cell is grown in an environment with both glucose and lactose. What happens to the expression of the lac operon?

Accepted Answer

The lac operon expression is diminished because glucose inhibits CAP activity.

Question 7

Which of the following is true about the CAP-cAMP complex in lac operon regulation?

Accepted Answer

It forms when cAMP levels are high, which occurs when glucose is absent.

Question 8

Which of the following best explains why humans and chimpanzees, despite sharing 98% genome similarity, are dramatically different?

Accepted Answer

Differences in gene expression patterns.

Question 9

What is the consequence of a mutation in the operator sequence (OC) of the lac operon?

Accepted Answer

The repressor cannot bind, leading to constitutive expression of the operon.

Question 10

Which of the following is a characteristic of an inducible system in prokaryotic gene regulation?

Accepted Answer

Transcription occurs only when a specific inducer is present.

Question 11

If a mutation causes the lac repressor protein to lose its ability to bind lactose, what is the expected outcome for lac operon expression?

Accepted Answer

The operon will be permanently repressed, even when lactose is present.

Question 12

Which of the following best describes polycistronic mRNA?

Accepted Answer

An mRNA that encodes multiple proteins from a single transcript.

Question 13

Which of the following is NOT a function of gene regulation in cells?

Accepted Answer

Increasing mutation rates.

Question 14

Which of the following is the correct sequence of events for gene expression in the lac operon?

Accepted Answer

Transcription → Translation → Protein production

Question 15

Which of the following statements about the lac operon is correct?

Accepted Answer

The lac operon is activated when lactose is present and glucose is absent.

Question 16

Which of the following best describes the effect of glucose on lac operon expression?

Accepted Answer

Glucose inhibits adenyl cyclase, decreasing cAMP levels and repressing the operon.

Question 17

Which of the following is a real-world application of understanding the lac operon system?

Accepted Answer

Designing antibiotics that target bacterial gene regulation.

Question 18

Which of the following is true about the relationship between the coding strand and the mRNA sequence?

Accepted Answer

The coding strand has the same sequence as the mRNA, except T replaces U.

Question 19

Which of the following best describes a repressible system in prokaryotic gene regulation?

Accepted Answer

Transcription is stopped when a specific substance (corepressor) is present.

Regulation of Gene Expression in Bacteria: The lac Operon

Study Guide - Practice Questions