Question 1

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

Accepted Answer

DNA contains deoxyribose sugar and is double-stranded and stable, while RNA contains ribose sugar and is usually single-stranded and less stable.

Question 2

A mutation occurs in the -10 consensus sequence of a bacterial promoter. What is the most likely effect on transcription?

Accepted Answer

Transcription initiation will likely decrease because the -10 region is critical for promoter recognition by RNA polymerase.

Question 3

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

Accepted Answer

It provides specificity for promoter recognition, allowing RNA polymerase to initiate transcription at the correct site.

Question 4

Given the following DNA template strand sequence (3'-TACGGTACG-5'), what is the corresponding mRNA sequence produced during transcription?

Accepted Answer

$$5'	ext{AUGCCAUGC}3'$$

Question 5

Which of the following is NOT a class of RNA involved in gene expression regulation?

Accepted Answer

rRNA

Question 6

In eukaryotic cells, which RNA polymerase is primarily responsible for transcribing protein-coding genes?

Accepted Answer

RNA polymerase II

Question 7

A researcher discovers a eukaryotic gene with multiple TATA boxes and CAAT boxes in its promoter region. What is the most likely significance of this arrangement?

Accepted Answer

It enables the gene to use alternative promoters, resulting in tissue-specific expression.

Question 8

Which of the following best explains why RNA is generally less stable than DNA?

Accepted Answer

RNA is single-stranded and contains a 2'-hydroxyl group on the ribose, making it more susceptible to hydrolysis.

Question 9

Which of the following is a correct sequence of events in eukaryotic mRNA processing?

Accepted Answer

5' capping, 3' polyadenylation, intron splicing

Question 10

A mutation in a eukaryotic gene prevents the addition of the 5' cap to its mRNA. What is the most likely consequence?

Accepted Answer

The mRNA will be rapidly degraded and not efficiently translated.

Question 11

Which of the following best describes the role of enhancers in eukaryotic transcription?

Accepted Answer

They are DNA elements that increase transcription by facilitating the binding of transcription factors and RNA polymerase.

Question 12

A patient has a mutation in the gene encoding the Rho protein in bacteria. Which process is most likely to be affected?

Accepted Answer

Rho-dependent transcription termination

Question 13

Which of the following is a key difference between prokaryotic and eukaryotic transcription and translation?

Accepted Answer

In prokaryotes, transcription and translation can occur simultaneously, while in eukaryotes, transcription occurs in the nucleus and translation in the cytoplasm.

Question 14

Which of the following best describes the function of small nuclear RNAs (snRNAs)?

Accepted Answer

They are involved in the splicing of pre-mRNA in eukaryotes.

Question 15

A gene is transcribed from the DNA template strand 3'-TACGAT-5'. What is the sequence of the coding (nontemplate) strand?

Accepted Answer

$$5'	ext{ATGCTA}3'$$

Question 16

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 17

Which of the following best explains the importance of consensus sequences in promoters?

Accepted Answer

They are specific DNA sequences recognized by transcription factors and RNA polymerase to initiate transcription.

Question 18

A mutation eliminates the polyadenylation signal in a eukaryotic gene. What is the most likely effect on the mRNA produced?

Accepted Answer

The mRNA will not receive a poly(A) tail, leading to decreased stability and inefficient export from the nucleus.

Question 19

Which of the following is a property shared by both DNA and RNA polymerases?

Accepted Answer

Both synthesize nucleic acids in the 5' to 3' direction.

Question 20

Which of the following best describes the effect of chromatin compaction on gene expression in eukaryotes?

Accepted Answer

Highly compacted chromatin (heterochromatin) is generally transcriptionally inactive.

DNA Structure, RNA Structure, and Transcription: Molecular Basis and Mechanisms

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