$$\text{DNA} \rightarrow \text{RNA} \rightarrow \text{Protein}$$

Question 1

Which of the following best describes the function of the operator region in a bacterial operon?

Accepted Answer

It is the site where regulatory proteins, such as repressors, bind to control transcription.

Question 2

In the absence of tryptophan, what is the state of the repressor protein in the trp operon?

Accepted Answer

The repressor is inactive and does not bind to the operator, allowing transcription.

Question 3

Which equation best represents the central dogma of molecular biology?

Accepted Answer

$$	ext{DNA} ightarrow 	ext{RNA} ightarrow 	ext{Protein}$$

Question 4

What is the effect of adding excess tryptophan to a bacterial culture on the trp operon?

Accepted Answer

Transcription of the trp operon decreases, as the repressor becomes active and binds to the operator.

Question 5

Which of the following statements about the lac operon is TRUE when lactose is present and glucose is absent?

Accepted Answer

Allolactose inactivates the repressor, cAMP levels are high, CAP is active, and transcription is maximized.

Question 6

Which of the following best explains diauxic growth in E. coli when both glucose and lactose are present?

Accepted Answer

E. coli uses glucose first, then switches to lactose after a lag phase.

Question 7

What is the role of cAMP in the regulation of the lac operon?

Accepted Answer

cAMP binds to CAP, activating it, which enhances RNA polymerase binding to the promoter.

Question 8

Which of the following is a consequence of a mutation that abolishes the affinity of the Lac I repressor for the operator?

Accepted Answer

Transcription of the lac operon will be constitutive, regardless of the presence or absence of lactose.

Question 9

Which of the following is NOT a feature of bacterial chromosomes?

Accepted Answer

Bacterial chromosomes contain introns that interrupt coding sequences.

Question 10

In quorum sensing, what triggers the activation of gene expression in Vibrio fischeri?

Accepted Answer

High concentration of autoinducer molecules inside the cell binds to LuxR, activating transcription.

Question 11

Which of the following best describes the function of polycistronic mRNA in bacteria?

Accepted Answer

It encodes multiple proteins from multiple genes within a single mRNA molecule.

Question 12

Which of the following is TRUE regarding the regulation of gene expression in bacteria?

Accepted Answer

Induction turns on gene expression in response to specific substances.

Question 13

What is the effect of a mutation that prevents CAP from binding to the CAP-binding site in the lac operon?

Accepted Answer

Transcription of the lac operon will be reduced even when lactose is present and glucose is absent.

Question 14

Which of the following statements about the Shine-Dalgarno sequence is correct?

Accepted Answer

It is a sequence in mRNA that binds to ribosomal RNA to initiate translation.

Question 15

Which of the following is a real-world consequence of the absence of introns in bacterial genes?

Accepted Answer

Bacteria can rapidly produce proteins, contributing to fast growth rates.

Question 16

Which of the following best describes negative control of gene expression?

Accepted Answer

A regulatory protein binds to the operator and inhibits transcription.

Question 17

Which of the following is TRUE about the Lux operon in Vibrio fischeri?

Accepted Answer

The Lux operon is activated by an autoinducer binding to LuxR, which then binds to the activator binding site.

Question 18

Which of the following best explains why clustered genes in bacterial chromosomes increase efficiency?

Accepted Answer

Clustered genes allow for simultaneous regulation of functionally related genes, reducing energy consumption.

Question 19

Which of the following is a correct description of the role of galactoside permease in the lac operon?

Accepted Answer

It transports lactose across the cell membrane into the cell.

Microbial Genetics: Structure, Function, and Regulation of Genetic Material

Study Guide - Practice Questions