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

Question 1

Which of the following best describes the function of the lac operon in E. coli?

Accepted Answer

It encodes enzymes for the uptake and metabolism of lactose.

Question 2

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

Accepted Answer

It binds to the repressor, causing it to dissociate from the operator and allowing transcription.

Question 3

Which of the following equations correctly represents the hydrolysis of lactose by β-galactosidase?

Accepted Answer

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

Question 4

In the presence of both glucose and lactose, what is the expected level of lac operon transcription in E. coli?

Accepted Answer

Low, because glucose inhibits cAMP production and CAP binding.

Question 5

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

Accepted Answer

lacY

Question 6

What is the effect of DNA methylation on gene expression in eukaryotes?

Accepted Answer

It decreases transcription by making DNA less accessible to transcription factors.

Question 7

Which of the following best explains why heart-specific proteins are only expressed in heart cells?

Accepted Answer

Gene expression is regulated so that only heart cells transcribe heart-specific genes.

Question 8

Which of the following statements about the catabolite activator protein (CAP) is correct?

Accepted Answer

CAP requires cAMP to bind to its site and activate transcription.

Question 9

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

Accepted Answer

The operon will be constitutively expressed, regardless of lactose presence.

Question 10

Which of the following modifications to histones is associated with increased gene expression?

Accepted Answer

Acetylation

Question 11

Which of the following best describes an operon?

Accepted Answer

A cluster of genes under the control of a single promoter.

Question 12

Which of the following is the correct sequence of events when lactose is added to E. coli growing in the absence of glucose?

Accepted Answer

Allolactose binds to the repressor, repressor dissociates, cAMP-CAP binds, RNA polymerase transcribes the operon.

Question 13

Which of the following is a direct product of the lacZ gene?

Accepted Answer

β-Galactosidase

Question 14

Which of the following best explains why not all genes are expressed at all times in a cell?

Accepted Answer

Gene regulation allows cells to conserve energy and resources by expressing genes only when needed.

Question 15

Which of the following is true regarding the operator region of the lac operon?

Accepted Answer

It is the binding site for the lac repressor protein.

Question 16

A researcher adds a chemical that prevents acetylation of histones in a eukaryotic cell. What is the most likely effect on gene expression?

Accepted Answer

Gene expression will decrease due to tighter DNA-histone interactions.

Question 17

Which of the following best describes the relationship between cAMP and glucose in the regulation of the lac operon?

Accepted Answer

Low glucose leads to high cAMP, which activates CAP and increases transcription.

Question 18

Which of the following is an example of a constitutive gene?

Accepted Answer

A gene encoding a ribosomal protein required for all cellular functions.

Question 19

Which of the following best explains the importance of gene regulation in multicellular organisms?

Accepted Answer

It enables cell differentiation and the development of specialized tissues.

Regulation of Gene Expression: Prokaryotic and Eukaryotic Mechanisms

Study Guide - Practice Questions