Question 1

Which of the following best describes the role of the sigma (σ) factor in prokaryotic transcription initiation?

Accepted Answer

It recognizes and binds to the –35 and –10 promoter regions, positioning RNA polymerase for transcription initiation.

Question 2

A mutation changes the –10 (Pribnow box) sequence from 5′–TATAAT–3′ to 5′–TATGGT–3′ in a bacterial promoter. What is the most likely effect on transcription?

Accepted Answer

Transcription initiation will be less efficient because the promoter is less easily recognized and unwound.

Question 3

During prokaryotic transcription, which DNA strand serves as the template for RNA synthesis, and in what direction is the RNA synthesized?

Accepted Answer

The template strand; RNA is synthesized 5′ → 3′

Question 4

Which of the following sequences is most likely to be found immediately downstream of a rho-independent terminator in a prokaryotic gene?

Accepted Answer

A GC-rich inverted repeat followed by a string of adenines in the DNA

Question 5

If the coding strand of a gene is 5′–ATGCGTACG–3′, what is the sequence of the mRNA transcribed from this region?

Accepted Answer

5′–AUGCGUACG–3′

Question 6

Which of the following best explains why transcription and translation can occur simultaneously in prokaryotes but not in eukaryotes?

Accepted Answer

Prokaryotes lack a nuclear envelope, allowing ribosomes to access mRNA as it is being transcribed.

Question 7

A researcher identifies a DNA sequence in E. coli with the following features: a –35 box (TTGACA), a –10 box (TATAAT), and a +1 site. Which of the following statements is correct regarding this sequence?

Accepted Answer

The +1 site marks the first nucleotide that will be transcribed into RNA.

Question 8

Which of the following events occurs during the elongation phase of prokaryotic transcription?

Accepted Answer

RNA polymerase synthesizes RNA in the 5′ → 3′ direction, and the sigma factor dissociates.

Question 9

Which of the following best describes the function of the 5′ untranslated region (5′ UTR) in prokaryotic mRNA?

Accepted Answer

It helps ribosomes bind to the mRNA for translation initiation.

Question 10

A mutation eliminates the rut site in a prokaryotic gene. Which process will be directly affected?

Accepted Answer

Rho-dependent termination of transcription

Question 11

Which of the following is true regarding the directionality of transcription in prokaryotes?

Accepted Answer

RNA is synthesized in the 5′ → 3′ direction using the template strand (3′ → 5′) as a template.

Question 12

Which of the following features is NOT typically found in a prokaryotic promoter region?

Accepted Answer

A start codon

Question 13

A prokaryotic gene has a strong A/T-rich –10 box and optimal spacing between the –35 and –10 regions. What is the expected effect on transcription?

Accepted Answer

Transcription will be highly efficient due to strong promoter recognition.

Question 14

Which of the following best explains why the coding strand is used to describe gene sequences?

Accepted Answer

It has the same sequence as the mRNA (except T is replaced by U), making it easier to interpret the genetic code.

Question 15

Which of the following is a key difference between rho-independent and rho-dependent termination in prokaryotic transcription?

Accepted Answer

Rho-dependent termination requires the rho protein to unwind the RNA–DNA hybrid, while rho-independent relies on a hairpin loop and poly-U sequence.

Question 16

A bacterial gene has the following sequence near its promoter: 5′–TTGACA–17bp–TATAAT–5′. What is the significance of the 17 base pairs between these two elements?

Accepted Answer

They provide optimal spacing for sigma factor binding and efficient transcription initiation.

Question 17

Which of the following best describes the fate of the sigma factor during prokaryotic transcription?

Accepted Answer

It dissociates from the core enzyme after initiation, allowing elongation to proceed.

Question 18

A scientist is analyzing a prokaryotic gene and finds a GC-rich inverted repeat followed by a string of adenines in the DNA. What is the most likely function of this sequence?

Accepted Answer

It serves as a rho-independent transcription terminator.

Question 19

Which of the following equations correctly represents the central dogma of molecular biology?

Accepted Answer

$$DNA \rightarrow RNA \rightarrow Protein$$

Transcription in Prokaryotes: Mechanisms and Gene Structure

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