Question 1

Which of the following best explains why RNA polymerase does not require a primer to initiate RNA synthesis, unlike DNA polymerase?

Accepted Answer

RNA polymerase can start synthesis de novo by recognizing promoter sequences and directly incorporating the first nucleotide.

Question 2

What are the two primary chemical differences between RNA and DNA nucleotides?

Accepted Answer

RNA contains uracil instead of thymine, and ribose instead of deoxyribose.

Question 3

In a standard bacterial promoter, what is the functional role of the Pribnow box (−10 sequence)?

Accepted Answer

It recruits the sigma factor and facilitates DNA unwinding for transcription initiation.

Question 4

Which structural motif forms in the RNA during intrinsic (Rho-independent) transcription termination in bacteria?

Accepted Answer

A stem-loop (hairpin) structure followed by a poly-U sequence.

Question 5

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

Accepted Answer

It recognizes promoter sequences and directs RNA polymerase to the correct transcription start site.

Question 6

Which nuclear RNA polymerase in eukaryotic cells is most sensitive to $$b-$$Amanitin?

Accepted Answer

RNA Polymerase II

Question 7

Which sequence element is typically located about 25–30 base pairs upstream of the transcription start site in a eukaryotic RNA Polymerase II core promoter?

Accepted Answer

TATA box

Question 8

During the assembly of General Transcription Factors (GTFs) at a core promoter, which factor is responsible for unwinding DNA and phosphorylating the C-terminal domain (CTD) of RNA Polymerase II?

Accepted Answer

TFIIH

Question 9

What is the significance of phosphorylation of the C-terminal domain (CTD) of RNA Polymerase II?

Accepted Answer

It coordinates cotranscriptional processing events such as capping, splicing, and cleavage/polyadenylation.

Question 10

Which modification is added to the 5' end of eukaryotic mRNA, and what is its primary function?

Accepted Answer

A 7-methylguanosine cap; it protects mRNA from degradation and facilitates translation initiation.

Question 11

Which consensus sequence is found at the branch-point Adenine during splicing, and what is its role?

Accepted Answer

The sequence 'CUAAG' marks the branch-point Adenine, which initiates the first transesterification reaction forming the lariat intron.

Question 12

Which snRNPs are directly involved in catalyzing the two transesterification reactions during splicing?

Accepted Answer

U1, U2, U4/U6, and U5

Question 13

Where is the Exon Junction Complex (EJC) deposited after splicing, and why is it important?

Accepted Answer

At the boundary of exons; it is essential for nuclear export via NXF1 and cytoplasmic quality control.

Question 14

How does alternative splicing contribute to protein diversity in eukaryotic cells?

Accepted Answer

It allows a single pre-mRNA transcript to generate multiple distinct protein isoforms by including or excluding different exons.

Question 15

Which process describes the rearrangement of exons between different genes to create new protein combinations?

Accepted Answer

Exon shuffling

Question 16

A mutation disrupts the consensus sequence at the 5' splice site of a pre-mRNA. What is the most likely consequence?

Accepted Answer

The intron will not be properly removed, leading to aberrant mRNA and potentially nonfunctional protein.

Question 17

Which of the following best describes the post-transcriptional processing of pre-rRNA in the nucleolus?

Accepted Answer

Pre-rRNA is cleaved, chemically modified, and assembled with ribosomal proteins to form mature ribosomal subunits.

Question 18

A patient is exposed to $$b-$$Amanitin, a potent inhibitor of RNA polymerase II. Which cellular process is most directly affected?

Accepted Answer

Synthesis of mRNA

Question 19

Which of the following steps occurs LAST during the assembly of General Transcription Factors (GTFs) and RNA Polymerase II at a core promoter?

Accepted Answer

Recruitment of TFIIH, which unwinds DNA and phosphorylates the CTD.

Cell Biology Study Guide: Transcription and RNA Processing

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