Q: Which equation correctly represents the directionality of RNA synthesis by RNA polymerase?

$$\text{RNA grows 5' \rightarrow 3'}$$

Question 1

Which of the following statements best distinguishes DNA replication from transcription in eukaryotic cells?

Accepted Answer

DNA replication creates a permanent DNA copy from one DNA template, which is amplified in future generations, while transcription produces many transient RNA copies that are eventually degraded.

Question 2

In a mammalian cell, approximately how many mRNA molecules are present, and what is the typical length of these molecules?

Accepted Answer

About 10,000 mRNA molecules, each around 2 kb in length.

Question 3

Which strand of DNA is used as the template for mRNA synthesis during transcription?

Accepted Answer

The template strand, which is complementary to the mRNA sequence.

Question 4

Given the DNA sequence below, which is the correct mRNA sequence transcribed from the template strand?

DNA sense strand: $$5'\ ATGCGTC\ 3'$$
DNA template strand: $$3'\ TACGCAG\ 5'$$

Accepted Answer

$$5'\ AUGCGUC\ 3'$$

Question 5

Which of the following best describes a monocistronic mRNA?

Accepted Answer

An RNA molecule that contains a single ORF, typical in eukaryotes.

Question 6

Which of the following is NOT a regulatory step in eukaryotic gene expression as depicted in the provided diagram?

Accepted Answer

DNA replication control

Question 7

A mutation in the promoter region of a gene most likely affects which aspect of gene expression?

Accepted Answer

The quantity of RNA produced from the allele, either increasing or decreasing expression.

Question 8

Which of the following best explains the role of sigma factors in prokaryotic transcription?

Accepted Answer

Sigma factors determine the binding specificity of RNA polymerase to promoter DNA, allowing recognition of consensus sequences.

Question 9

What is the consequence of a hypermorphic mutation in a promoter region?

Accepted Answer

Increase in RNA polymerase affinity, leading to increased gene expression.

Question 10

Which of the following is a feature of a strong intrinsic (rho-independent) transcription terminator in prokaryotes?

Accepted Answer

A region rich in G-C pairs forming a stem-loop structure followed by a U-rich sequence.

Question 11

During transcription initiation in prokaryotes, what is the significance of the closed and open complex formation?

Accepted Answer

The open complex involves melting of DNA around the -10 region, allowing the template strand to enter the enzyme active site.

Question 12

Which equation correctly represents the directionality of RNA synthesis by RNA polymerase?

Accepted Answer

$$	ext{RNA grows 5' ightarrow 3'}$$

Question 13

Which of the following best describes abortive initiation during transcription?

Accepted Answer

RNA polymerase synthesizes short RNA fragments that are released before promoter escape.

Question 14

A mutation in the sigma factor gene that alters its ability to recognize the consensus sequence will most likely:

Accepted Answer

Affect the expression of all genes controlled by that sigma factor.

Question 15

Which of the following is true regarding the consensus sequence recognized by sigma factors?

Accepted Answer

It represents the most frequent residues at each position among a group of promoters.

Question 16

Which of the following statements about the role of the TATA box in transcription is correct?

Accepted Answer

The TATA box is a promoter element that facilitates DNA melting and open complex formation.

Question 17

Which of the following best describes the difference between a strong and weak promoter?

Accepted Answer

A strong promoter has high homology with the consensus sequence and optimal spacing, increasing RNA polymerase affinity.

Question 18

Which of the following is a direct result of transcription termination by the Rho protein in prokaryotes?

Accepted Answer

Rho protein binds to a specific site on nascent RNA and uses helicase activity to unwind the RNA-DNA hybrid, releasing the RNA.

Question 19

Which of the following best explains why transcription initiation is often the rate-limiting step in gene expression?

Accepted Answer

It requires assembly of the transcription apparatus and is subject to multiple regulatory mechanisms.

Prokaryotic Transcription: Mechanisms, Regulation, and Comparison with Replication

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