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

Question 1

Which of the following best describes the role of the sigma factor in bacterial transcription initiation?

Accepted Answer

It recognizes and binds to the promoter sequence, guiding RNA polymerase to the correct start site.

Question 2

During transcription elongation in bacteria, which direction does RNA polymerase synthesize the new RNA strand?

Accepted Answer

5' to 3'

Question 3

What is the primary difference between transcription termination in bacteria and eukaryotes?

Accepted Answer

Eukaryotes use a poly(A) signal, while bacteria use a terminator sequence that forms a hairpin structure in the RNA.

Question 4

Which equation correctly represents the central dogma of molecular biology?

Accepted Answer

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

Question 5

In the lac operon, what happens when lactose is present and glucose is absent?

Accepted Answer

CAP is activated by cAMP and binds to the promoter, enhancing transcription of the lac genes.

Question 6

Which of the following best explains why gene expression must be regulated in multicellular organisms?

Accepted Answer

To allow different cell types to perform specialized functions by expressing only certain genes.

Question 7

Which of the following is a correct statement about the regulation of gene expression?

Accepted Answer

Gene expression can be regulated at multiple steps, including transcription, translation, and post-translational modification.

Question 8

A mutation in the lacI gene of E. coli results in a nonfunctional repressor protein. What is the most likely consequence?

Accepted Answer

The lac operon will be transcribed continuously, regardless of lactose presence.

Question 9

Which of the following best describes the effect of glucose on the lac operon?

Accepted Answer

Glucose decreases cAMP levels, preventing CAP from activating transcription of the lac operon.

Question 10

Which of the following is true regarding eukaryotic transcription compared to bacterial transcription?

Accepted Answer

Eukaryotes have multiple RNA polymerases and more complex promoter regions, such as the TATA box.

Question 11

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

Accepted Answer

Low glucose, high lactose

Question 12

What is the function of the operator region in the lac operon?

Accepted Answer

It is the site where the repressor protein binds to block transcription.

Question 13

Which of the following best describes allosteric regulation in the context of the lac operon?

Accepted Answer

Lactose binds to the repressor, changing its shape and reducing its affinity for the operator.

Question 14

Which of the following is a correct sequence of events during bacterial transcription initiation?

Accepted Answer

Sigma factor binds to RNA polymerase, the holoenzyme binds to the promoter, and transcription begins.

Question 15

Which of the following equations correctly represents the relationship between cAMP and CAP activation in the lac operon?

Accepted Answer

$$	ext{Low glucose} ightarrow 	ext{High cAMP} ightarrow 	ext{CAP activation}$$

Question 16

A researcher adds a molecule that mimics lactose to an E. coli culture. What is the expected effect on the lac operon?

Accepted Answer

The repressor will be released from the operator, allowing transcription of the lac operon.

Question 17

Which of the following is a real-world example of gene expression regulation in human cells?

Accepted Answer

Muscle cells express genes for contractile proteins, while immune cells express genes for antibodies.

Question 18

Which of the following statements about transcription factors is correct?

Accepted Answer

Transcription factors bind to DNA and regulate the initiation of transcription.

Question 19

Which of the following best explains why the lac operon is considered an example of both negative and positive regulation?

Accepted Answer

It is regulated by both a repressor (negative control) and an activator protein CAP (positive control).

Transcription and Regulation of Gene Expression in Bacteria and Eukaryotes

Study Guide - Practice Questions