Question 1

Which of the following statements best describes the difference between RNA and DNA nucleotides?

Accepted Answer

RNA nucleotides use uracil instead of thymine and contain ribose as the sugar.

Question 2

During the pulse-chase experiment in bacteria by Volkin and Astrachan, what was the key observation that led to the conclusion that RNA transcription is necessary for new phage protein formation?

Accepted Answer

A burst of transcriptional activity was observed, followed by rapid breakdown of RNA molecules.

Question 3

Which of the following types of RNA is the only one that undergoes translation?

Accepted Answer

Messenger RNA (mRNA)

Question 4

A mutation in the Pribnow box (–10 consensus sequence) of a bacterial promoter would most likely result in which of the following?

Accepted Answer

Reduced or abolished transcription initiation due to poor RNA polymerase binding.

Question 5

Which of the following best describes the function of the sigma ($$ \sigma ) $$subunit in bacterial RNA polymerase?

Accepted Answer

It recognizes promoter sequences and facilitates binding of RNA polymerase to DNA.

Question 6

Which of the following is a correct sequence of events during bacterial transcription initiation?

Accepted Answer

RNA polymerase binds loosely to the promoter, forms the closed promoter complex, then unwinds DNA to form the open promoter complex.

Question 7

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

Accepted Answer

Initiating polyadenylation at the 3' end.

Question 8

A researcher mutates the branch point adenine in a eukaryotic pre-mRNA intron. What is the most likely consequence?

Accepted Answer

Splicing will be disrupted, and the intron will not be properly removed.

Question 9

Which of the following best explains why eukaryotic cells can produce more distinct polypeptides than the number of genes in their genome?

Accepted Answer

Alternative splicing, alternative promoters, and alternative polyadenylation allow for multiple mRNA products from a single gene.

Question 10

Which of the following is a key feature of intrinsic (Rho-independent) termination of transcription in bacteria?

Accepted Answer

A hairpin structure forms in the mRNA followed by a string of uracils, causing RNA polymerase to dissociate.

Question 11

A patient is treated with rifampicin, which inhibits bacterial RNA polymerase. Which of the following processes will be directly affected in the bacteria?

Accepted Answer

Transcription of mRNA, tRNA, and rRNA

Question 12

Which of the following correctly matches a eukaryotic RNA polymerase with its primary function?

Accepted Answer

RNA polymerase II: transcribes protein-coding genes

Question 13

Which of the following is a function of the poly-A tail added to eukaryotic mRNA?

Accepted Answer

Facilitates transport of mature mRNA to the cytoplasm and protects mRNA from degradation.

Question 14

A mutation in the CAAT box of a eukaryotic promoter is most likely to have which effect?

Accepted Answer

Reduced transcription due to decreased binding of transcription factors.

Question 15

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

Accepted Answer

They increase transcription by binding activator proteins and facilitating interaction with the transcription complex.

Question 16

Which of the following is true regarding the processing of eukaryotic pre-mRNA?

Accepted Answer

The carboxyl terminal domain (CTD) of RNA polymerase II coordinates capping, splicing, and polyadenylation.

Question 17

A gene contains six exons and two alternative polyadenylation sites. In thyroid cells, polyadenylation occurs after exon 4, while in neuronal cells, it occurs after exon 6. What is the most likely result?

Accepted Answer

Thyroid cells produce a shorter mRNA encoding calcitonin, while neuronal cells produce a longer mRNA encoding CGRP.

Question 18

Which of the following statements about self-splicing introns is correct?

Accepted Answer

Group I and Group II introns can catalyze their own excision from RNA transcripts.

Question 19

A mutation that disrupts the function of the internal control region (ICR) in a tRNA gene would most likely affect which process?

Accepted Answer

Binding of RNA polymerase III and transcription of the tRNA gene.

8. Molecular Biology of Transcription and RNA Processing

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