Question 1

Which of the following best describes the central dogma of molecular biology as depicted in the first image?

Accepted Answer

DNA is replicated, transcribed into RNA, and then translated into protein.

Question 2

During transcription in prokaryotes, which enzyme is responsible for synthesizing RNA from a DNA template?

Accepted Answer

RNA polymerase

Question 3

What is the main functional difference between the core enzyme and the holoenzyme of prokaryotic RNA polymerase?

Accepted Answer

The holoenzyme can initiate transcription due to the presence of the sigma factor, while the core enzyme cannot.

Question 4

Which of the following statements about operons is correct?

Accepted Answer

Operons allow multiple genes to be transcribed from a single promoter, resulting in polycistronic mRNA.

Question 5

Which of the following best explains why RNA polymerase is less accurate than DNA polymerase?

Accepted Answer

Errors in RNA are less critical because RNA is not inherited and is often short-lived.

Question 6

In the context of transcription, what is the significance of the consensus promoter sequence?

Accepted Answer

It represents the most common nucleotides at each position, providing the strongest binding for RNA polymerase.

Question 7

Which of the following is a key feature of intrinsic (rho-independent) transcription termination in E. coli?

Accepted Answer

A GC-rich region forms a stable hairpin followed by a stretch of Us.

Question 8

Why did scientists suspect the existence of the Rho factor in transcription termination?

Accepted Answer

RNA produced in vitro was longer than RNA made in vivo, suggesting an accessory protein was missing.

Question 9

Which of the following equations correctly represents the direction of RNA synthesis during transcription?

Accepted Answer

$$5' \rightarrow 3'$$

Question 10

Which sigma factor is primarily responsible for recognizing the housekeeping promoters in E. coli?

Accepted Answer

Sigma 70 ($$\$$sigma^{70}$$)

Question 11

Which of the following is NOT a similarity between DNA polymerase and RNA polymerase?

Accepted Answer

Both require a primer to initiate synthesis.

Question 12

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

Accepted Answer

It directs the RNA polymerase core enzyme to specific promoter sequences.

Question 13

A mutation in the -10 region of a bacterial promoter would most likely result in which of the following?

Accepted Answer

Decreased binding of RNA polymerase and lower transcription rates.

Question 14

Which of the following statements about monocistronic and polycistronic mRNA is correct?

Accepted Answer

Polycistronic mRNA is common in prokaryotes and allows coordinated expression of functionally related genes.

Question 15

Which of the following antibiotics inhibits transcription initiation by binding to the β subunit of prokaryotic RNA polymerase?

Accepted Answer

Rifampicin

Question 16

Which of the following is true regarding the directionality of the template and coding strands during transcription?

Accepted Answer

The template strand is read 3’ to 5’ and the RNA is synthesized 5’ to 3’.

Question 17

Which of the following best explains why both DNA strands can serve as templates for transcription, but not for the same gene?

Accepted Answer

Each gene has a specific promoter that determines which strand is used as the template.

Question 18

Which of the following is a function of the omega ($$\omega) $$subunit in the prokaryotic RNA polymerase core enzyme?

Accepted Answer

Assists in RNA polymerase assembly and stability.

Question 19

Which of the following is a reason why consensus promoter sequences are rarely found in real genomes?

Accepted Answer

Natural variation in promoter sequences allows for differential gene expression.

Transcription: Mechanisms and Regulation in Prokaryotes and Eukaryotes

Study Guide - Practice Questions