BIOL 271 MODULE 6 EXAM 2027
QUESTIONS AND ANSWERS
1. Which enzyme is responsible for relieving torsional strain ahead of the replication fork by
creating transient breaks in the DNA backbone?
A. DNA Helicase
B. DNA Primase
C. DNA Topoisomerase
D. Single-Strand Binding Proteins
Answer: C
Conceptual Explanation: Topoisomerases, such as DNA gyrase in prokaryotes, relieve the
supercoiling and torsional strain caused by the unwinding of the DNA double helix.
2. In DNA replication, which enzyme possesses 5’ to 3’ exonuclease activity to remove RNA
primers?
A. DNA Polymerase III
B. DNA Polymerase II
C. DNA Ligase
D. DNA Polymerase I
,Answer: D
Conceptual Explanation: DNA Polymerase I is unique because it has 5’ to 3’ exonuclease
activity, allowing it to remove RNA primers and replace them with DNA nucleotides.
3. What is the role of the sigma factor in bacterial transcription?
A. Catalyzing the formation of phosphodiester bonds
B. Terminating the transcription process
C. Recognizing and binding to the promoter region
D. Splicing out introns from the mRNA transcript
Answer: C
Conceptual Explanation: The sigma factor is a subunit of the bacterial RNA polymerase
holoenzyme that ensures the enzyme binds specifically to promoter sequences to initiate
transcription.
4. Which mechanism ensures the high fidelity of DNA replication?
A. Promoter recognition by TFIID
B. Alternative splicing of the lagging strand
C. Degradation of Okazaki fragments
D. 3’ to 5’ exonuclease activity of DNA Polymerases
Answer: D
, Conceptual Explanation: Proofreading is performed by the 3’ to 5’ exonuclease activity of
DNA polymerases, which removes incorrectly paired nucleotides at the end of a growing
chain.
5. During eukaryotic transcription, which general transcription factor binds directly to the
TATA box?
A. TFIIB
B. TFIIH
C. TFIIE
D. TFIID (via TBP)
Answer: D
Conceptual Explanation: TFIID contains the TATA-binding protein (TBP), which
recognizes and binds to the TATA box, initiating the assembly of the transcription initiation
complex.
6. What is the chemical nature of the 5’ cap added to eukaryotic mRNA?
A. A poly-adenosine tail
B. A 7-methylguanosine residue linked via a 5’-5’ triphosphate bridge
C. A sequence of 200 uracil nucleotides
D. A modified methionine residue
Answer: B
QUESTIONS AND ANSWERS
1. Which enzyme is responsible for relieving torsional strain ahead of the replication fork by
creating transient breaks in the DNA backbone?
A. DNA Helicase
B. DNA Primase
C. DNA Topoisomerase
D. Single-Strand Binding Proteins
Answer: C
Conceptual Explanation: Topoisomerases, such as DNA gyrase in prokaryotes, relieve the
supercoiling and torsional strain caused by the unwinding of the DNA double helix.
2. In DNA replication, which enzyme possesses 5’ to 3’ exonuclease activity to remove RNA
primers?
A. DNA Polymerase III
B. DNA Polymerase II
C. DNA Ligase
D. DNA Polymerase I
,Answer: D
Conceptual Explanation: DNA Polymerase I is unique because it has 5’ to 3’ exonuclease
activity, allowing it to remove RNA primers and replace them with DNA nucleotides.
3. What is the role of the sigma factor in bacterial transcription?
A. Catalyzing the formation of phosphodiester bonds
B. Terminating the transcription process
C. Recognizing and binding to the promoter region
D. Splicing out introns from the mRNA transcript
Answer: C
Conceptual Explanation: The sigma factor is a subunit of the bacterial RNA polymerase
holoenzyme that ensures the enzyme binds specifically to promoter sequences to initiate
transcription.
4. Which mechanism ensures the high fidelity of DNA replication?
A. Promoter recognition by TFIID
B. Alternative splicing of the lagging strand
C. Degradation of Okazaki fragments
D. 3’ to 5’ exonuclease activity of DNA Polymerases
Answer: D
, Conceptual Explanation: Proofreading is performed by the 3’ to 5’ exonuclease activity of
DNA polymerases, which removes incorrectly paired nucleotides at the end of a growing
chain.
5. During eukaryotic transcription, which general transcription factor binds directly to the
TATA box?
A. TFIIB
B. TFIIH
C. TFIIE
D. TFIID (via TBP)
Answer: D
Conceptual Explanation: TFIID contains the TATA-binding protein (TBP), which
recognizes and binds to the TATA box, initiating the assembly of the transcription initiation
complex.
6. What is the chemical nature of the 5’ cap added to eukaryotic mRNA?
A. A poly-adenosine tail
B. A 7-methylguanosine residue linked via a 5’-5’ triphosphate bridge
C. A sequence of 200 uracil nucleotides
D. A modified methionine residue
Answer: B
