Q: Which equation best represents the information flow in gene expression?

$$\text{DNA} \rightarrow \text{mRNA} \rightarrow \text{protein} \rightarrow \text{activated protein}$$

Q: Which equation represents the relationship between glucose, cAMP, and CAP activity in lac operon regulation?

$$[\text{glucose}] \downarrow \Rightarrow [\text{cAMP}] \uparrow \Rightarrow [\text{CAP-cAMP}] \uparrow$$

Question 1

Which of the following best describes the tradeoff between transcriptional, translational, and post-translational control of gene expression in bacteria?

Accepted Answer

Post-translational control is the fastest in response time but least efficient in resource use.

Question 2

In the lac operon, what is the role of the lac I gene product?

Accepted Answer

It codes for a repressor protein that binds the operator to shut off transcription of lac Z and lac Y.

Question 3

Which equation best represents the information flow in gene expression?

Accepted Answer

$$	ext{DNA} ightarrow 	ext{mRNA} ightarrow 	ext{protein} ightarrow 	ext{activated protein}$$

Question 4

What happens to the lac operon when lactose is present and glucose is absent?

Accepted Answer

The repressor protein is inactivated by lactose, and CAP-cAMP complex upregulates transcription.

Question 5

Which scenario would result in the highest expression of the lac operon genes?

Accepted Answer

Low glucose, high lactose

Question 6

A constitutive mutant of the lac operon produces β-galactosidase and galactoside permease regardless of lactose presence. Which gene is most likely mutated?

Accepted Answer

lac I

Question 7

Which of the following is an example of negative control of gene expression?

Accepted Answer

A repressor protein binds the operator and blocks RNA polymerase from transcribing the gene.

Question 8

What is the effect of glucose on the lac operon when both glucose and lactose are present?

Accepted Answer

Glucose inhibits lactose transport and reduces CAP activity, preventing lac operon expression.

Question 9

Which of the following best describes an operon?

Accepted Answer

A set of adjacent genes transcribed together under the control of a single promoter and regulatory molecule.

Question 10

If a mutation prevents the lac repressor from binding lactose, what is the expected outcome for lac operon expression?

Accepted Answer

The operon will never be expressed, even when lactose is present.

Question 11

Which equation represents the relationship between glucose, cAMP, and CAP activity in lac operon regulation?

Accepted Answer

$$[	ext{glucose}] \downarrow \Rightarrow [	ext{cAMP}] \uparrow \Rightarrow [	ext{CAP-cAMP}] \uparrow$$

Question 12

Which of the following is NOT a mechanism of gene regulation in bacteria?

Accepted Answer

Constitutive control

Question 13

A cell with a defective lac Y gene will most likely:

Accepted Answer

Be unable to transport lactose into the cell.

Question 14

Which of the following statements about global gene regulation is correct?

Accepted Answer

A regulon is a set of genes or operons controlled by a single regulatory protein.

Question 15

In an experiment, E. coli is grown in three conditions: glucose only, lactose only, and glucose + lactose. In which condition(s) is β-galactosidase produced?

Accepted Answer

Lactose only

Question 16

Which of the following best explains why E. coli prefers glucose over lactose?

Accepted Answer

Glucose is directly used in glycolysis, requiring fewer steps and less energy.

Question 17

What is the effect of inducer exclusion on the lac operon when glucose is present?

Accepted Answer

Glucose inhibits galactoside permease, preventing lactose transport and lac operon expression.

Question 18

Which of the following is a real-world application of understanding bacterial gene regulation?

Accepted Answer

Designing antibiotics that target regulatory proteins to inhibit bacterial growth.

CH. 18- Gene Regulation in Bacteria: Mechanisms and the lac Operon

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