Question 1

Which of the following statements best explains why RNA is able to leave the nucleus in eukaryotic cells, while DNA remains inside?

Accepted Answer

RNA is single-stranded and smaller, allowing it to pass through nuclear pores after processing.

Question 2

During transcription in bacteria, which sequence is recognized by the sigma subunit of RNA polymerase to initiate transcription?

Accepted Answer

The -10 consensus sequence (Pribnow box): $$5'-TATAAT-3'$$

Question 3

Which of the following is NOT a function of the 5' cap added to eukaryotic mRNA?

Accepted Answer

Initiating polyadenylation at the 3' end

Question 4

A mutation in the branch point adenine of an intron would most likely result in:

Accepted Answer

Failure to form the lariat structure during splicing

Question 5

Which enzyme is responsible for adding the poly-A tail to the 3' end of eukaryotic pre-mRNA?

Accepted Answer

Polyadenylate polymerase (PAP)

Question 6

Which of the following best describes the difference between intrinsic and rho-dependent termination in bacterial transcription?

Accepted Answer

Intrinsic termination relies on a hairpin structure in the mRNA, while rho-dependent termination requires the rho protein to release the transcript.

Question 7

A researcher isolates a bacterial strain that is resistant to rifampicin. Which of the following is the most likely explanation for this resistance?

Accepted Answer

The RNA polymerase of the strain has a mutation that prevents rifampicin from inhibiting the formation of the first phosphodiester bond.

Question 8

Which of the following is a direct result of alternative splicing in eukaryotic cells?

Accepted Answer

Production of multiple protein isoforms from a single gene

Question 9

Which RNA molecule acts as a template for the synthesis of repetitive DNA sequences at telomeres?

Accepted Answer

Telomerase RNA

Question 10

A mutation eliminates the -35 consensus sequence in a bacterial promoter. What is the most likely effect on transcription?

Accepted Answer

RNA polymerase holoenzyme binding to the promoter will be greatly reduced, decreasing transcription initiation.

Question 11

Which of the following best explains why eukaryotic mRNAs are generally more stable than bacterial mRNAs?

Accepted Answer

Eukaryotic mRNAs undergo posttranscriptional modifications such as 5' capping and 3' polyadenylation.

Question 12

Which of the following is a function of small nuclear RNAs (snRNAs) in eukaryotic cells?

Accepted Answer

They participate in the splicing of pre-mRNA by forming part of the spliceosome.

Question 13

Which of the following accurately describes the role of enhancer sequences in eukaryotic transcription?

Accepted Answer

They bind activator proteins and coactivators, forming a protein bridge that increases RNA polymerase II efficiency.

Question 14

Which of the following best describes the evolutionary relationship between archaeal and eukaryotic transcription machinery?

Accepted Answer

Archaeal RNA polymerase and promoter structure are more similar to those of eukaryotes than to bacteria.

Question 15

A patient has a genetic disorder that results in the loss of function of poly-A-binding protein II (PABII). Which of the following cellular processes would be most directly affected?

Accepted Answer

The rate of polyadenylation of mRNA would decrease, reducing mRNA stability.

Question 16

Which of the following is a direct consequence of the 'torpedo model' of eukaryotic transcription termination?

Accepted Answer

A specialized RNase digests the residual transcript, causing RNA polymerase II to release from DNA.

Question 17

Which of the following is true regarding group I and group II introns?

Accepted Answer

Both are self-splicing ribozymes that do not require the spliceosome for removal.

Question 18

Which of the following best explains the phenomenon where human cells produce over 100,000 distinct polypeptides from approximately 22,000 genes?

Accepted Answer

Alternative splicing, alternative promoters, and alternative polyadenylation sites generate multiple mRNAs from a single gene.

Question 19

Which of the following is a real-life example of RNA editing by base substitution in humans?

Accepted Answer

Production of two different apolipoprotein B proteins from a single gene in liver and intestinal cells

Molecular Biology of Transcription and RNA Processing 8

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