$$[\text{cAMP}] \propto \frac{1}{[\text{glucose}]}$$

Question 1

Which of the following best describes the primary mechanism by which prokaryotes regulate gene expression?

Accepted Answer

By altering the rate of transcription initiation

Question 2

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

Accepted Answer

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

Question 3

Which of the following scenarios will result in the highest level of lac operon transcription in E. coli?

Accepted Answer

Lactose present, glucose absent

Question 4

What is the function of the catabolite activator protein (CAP) in the regulation of the lac operon?

Accepted Answer

It facilitates RNA polymerase binding to the promoter when bound to cAMP

Question 5

Which of the following equations correctly represents the relationship between cAMP and glucose in E. coli?

Accepted Answer

$$[	ext{cAMP}] \propto \frac{1}{[	ext{glucose}]}$$

Question 6

A mutation in the lacI gene results in a nonfunctional repressor protein. What is the most likely outcome for the lac operon?

Accepted Answer

The operon will be constitutively expressed, regardless of lactose presence

Question 7

Which of the following best describes attenuation in the trp operon?

Accepted Answer

A mechanism where transcription is terminated early depending on tryptophan levels

Question 8

What is the effect of a corepressor on a repressible operon such as the trp operon?

Accepted Answer

It binds to the repressor, enabling it to bind the operator and block transcription

Question 9

Which of the following is a function of antisense RNA in prokaryotic gene regulation?

Accepted Answer

It can bind to mRNA and block translation initiation

Question 10

Which of the following statements about riboswitches is correct?

Accepted Answer

They are mRNA regions that change conformation upon ligand binding, affecting transcription or translation

Question 11

A bacterium is grown in a medium containing both glucose and lactose. What is the expected state of the lac operon?

Accepted Answer

Low transcription due to catabolite repression

Question 12

Which of the following best explains why the trp operon is considered a repressible operon?

Accepted Answer

It is usually on but can be turned off when tryptophan is abundant

Question 13

Which of the following is NOT a way that prokaryotes regulate gene expression?

Accepted Answer

By methylating cytosine residues in DNA to silence genes

Question 14

Which structural gene of the lac operon encodes the enzyme responsible for lactose uptake into the cell?

Accepted Answer

lacY

Question 15

A mutation causes the CAP protein to be unable to bind cAMP. What is the most likely effect on the lac operon?

Accepted Answer

Transcription will be low even if lactose is present and glucose is absent

Question 16

Which of the following best describes the function of the leader peptide (trpL) in the trp operon?

Accepted Answer

It is involved in attenuation by sensing tryptophan levels during translation

Question 17

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

Accepted Answer

A repressor protein binding to the operator to block transcription

Question 18

Which of the following is true regarding feedback inhibition in prokaryotic gene regulation?

Accepted Answer

The end product of a metabolic pathway inhibits the first enzyme in the pathway

Question 19

Which of the following best describes the organization of an operon?

Accepted Answer

A cluster of genes under the control of a single promoter, transcribed as a polycistronic mRNA

Regulation of Gene Expression in Prokaryotes: Operons, Riboswitches, and Antisense RNAs

Study Guide - Practice Questions