Question 1

Which of the following best describes the function of constitutive genes in bacterial cells?

Accepted Answer

They are expressed continuously and encode housekeeping functions.

Question 2

In the maltose catabolism pathway in E. coli, what is required for the maltose activator protein to bind DNA and activate transcription?

Accepted Answer

Binding of maltose (inducer) to the activator protein.

Question 3

Which equation best represents the relationship between the rate of transcription ($$R_t) $$and the presence of an activator protein ($$A) $$and inducer ($$I) in $$positive control?

Accepted Answer

$$R_t = k \cdot A \cdot I$$

Question 4

What is the primary role of a repressor protein in negative control of gene expression?

Accepted Answer

To block transcription by binding to the operator.

Question 5

Which scenario best illustrates enzyme induction in the lac operon?

Accepted Answer

Lactose is present, binds to the repressor, inactivates it, and transcription proceeds.

Question 6

During diauxic growth, what happens when two energy sources are available to E. coli?

Accepted Answer

The better energy source is consumed first, followed by a lag phase, then the second source is used.

Question 7

Which regulatory mechanism allows bacteria to preferentially use glucose over lactose?

Accepted Answer

Regulation by catabolite activator protein (CAP) in response to glucose presence.

Question 8

Attenuation in the trp operon is best described as:

Accepted Answer

Termination of transcription within the leader region based on tryptophan levels.

Question 9

Which equation describes the probability ($$P) of $$transcription continuation in the trp operon as a function of tryptophan concentration ($$[Trp]$$)?

Accepted Answer

$$P = \frac{1}{1 + [Trp]}$$

Question 10

How do riboswitches regulate gene expression in Gram-positive bacteria?

Accepted Answer

By altering mRNA folding to terminate transcription.

Question 11

Which statement best describes quorum sensing in bacteria?

Accepted Answer

It couples cell density and intercellular communication to transcription regulation via signaling molecules.

Question 12

In Vibrio fischeri, what triggers the activation of bioluminescence genes?

Accepted Answer

High concentrations of AHL binding to LuxR, which activates transcription.

Question 13

Which equation best models the relationship between cell density ($$D) $$and autoinducer concentration ($$A) in $$quorum sensing?

Accepted Answer

$$A = k \cdot D$$

Question 14

What is the primary function of CRISPR-associated (Cas) proteins in bacterial cells?

Accepted Answer

To cleave CRISPR RNA and destroy invading nucleic acids.

Question 15

Which process is illustrated by the equation $$crRNA + foreign\ DNA \rightarrow$$ destruction of foreign DNA?

Accepted Answer

CRISPR interference.

Question 16

Which of the following is a plausible consequence if a bacteriophage mutates its genome to avoid CRISPR recognition?

Accepted Answer

The bacterium will be unable to destroy the phage DNA.

Question 17

Which regulatory mechanism is most likely to be used by bacteria to rapidly respond to environmental changes in nutrient availability?

Accepted Answer

Inducible gene expression controlled by repressors and activators.

Question 18

Which statement best explains why riboswitches are considered sensory RNAs?

Accepted Answer

They sense and bind effector molecules, altering mRNA folding and gene expression.

Question 19

Which equation best represents the effect of an inducer ($$I) on $$repressor activity ($$R) in $$negative control?

Accepted Answer

$$R_{active} = R_{total} - I$$

Regulation of Bacterial Cellular Processes: Mechanisms and Examples

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