BIOL 331 EXAM 2: MOLECULAR
BIOLOGY AND CELLULAR PROCESSES
QUESTIONS & VERIFIED ANSWERS
2026/2027 UPDATE
1. During DNA replication, which enzyme is responsible for relieving the torsional strain
caused by the unwinding of the double helix?
A. Topoisomerase
B. DNA Polymerase III
C. DNA Helicase
D. Single-strand binding proteins
Answer: A
Conceptual Explanation: Topoisomerase (such as DNA gyrase in bacteria) acts ahead of
the replication fork to produce breaks in the DNA, relieving the supercoiling strain induced
by helicase.
2. Which of the following describes the mechanism by which DNA Polymerase ensures high
fidelity during replication?
A. 5’ to 3’ exonuclease activity
B. Mismatch repair protein recruitment
,C. RNA primase degradation
D. 3’ to 5’ exonuclease activity
Answer: D
Conceptual Explanation: DNA Polymerases possess 3’ to 5’ exonuclease activity, which
allows them to remove incorrectly paired nucleotides at the end of a growing strand, a
process known as proofreading.
3. In eukaryotic transcription, what is the role of the TATA-binding protein (TBP)?
A. It recruits RNA Polymerase III to the mitochondrial genome
B. It recognizes and binds the TATA box to initiate the assembly of the pre-initiation
complex
C. It facilitates the phosphorylation of the CTD of RNA Pol II
D. It acts as a helicase to open the promoter region
Answer: B
Conceptual Explanation: TBP is a subunit of TFIID that recognizes the TATA box sequence
in the promoter, serving as a scaffold for other general transcription factors and RNA Pol II.
4. Which modification occurs at the 5’ end of a eukaryotic mRNA molecule shortly after
transcription begins?
A. Addition of a poly-A tail
B. Splicing of the first intron
, C. Addition of a 7-methylguanosine cap
D. Binding of the sigma factor
Answer: C
Conceptual Explanation: The 5’ cap (7-methylguanosine) is added to the nascent mRNA
transcript to protect it from degradation and assist in ribosome binding.
5. What is the primary function of the sigma factor in prokaryotic transcription?
A. Elongation of the RNA chain
B. Termination of transcription at rho-independent sites
C. Catalyzing the formation of phosphodiester bonds
D. Recognition of specific promoter sequences (-10 and -35 boxes)
Answer: D
Conceptual Explanation: The sigma factor is a subunit of the bacterial RNA polymerase
holoenzyme that ensures the enzyme binds specifically to promoter regions to initiate
transcription.
6. During translation, which site of the ribosome does the initiator tRNA-Met first enter?
A. A site
B. E site
C. P site
BIOLOGY AND CELLULAR PROCESSES
QUESTIONS & VERIFIED ANSWERS
2026/2027 UPDATE
1. During DNA replication, which enzyme is responsible for relieving the torsional strain
caused by the unwinding of the double helix?
A. Topoisomerase
B. DNA Polymerase III
C. DNA Helicase
D. Single-strand binding proteins
Answer: A
Conceptual Explanation: Topoisomerase (such as DNA gyrase in bacteria) acts ahead of
the replication fork to produce breaks in the DNA, relieving the supercoiling strain induced
by helicase.
2. Which of the following describes the mechanism by which DNA Polymerase ensures high
fidelity during replication?
A. 5’ to 3’ exonuclease activity
B. Mismatch repair protein recruitment
,C. RNA primase degradation
D. 3’ to 5’ exonuclease activity
Answer: D
Conceptual Explanation: DNA Polymerases possess 3’ to 5’ exonuclease activity, which
allows them to remove incorrectly paired nucleotides at the end of a growing strand, a
process known as proofreading.
3. In eukaryotic transcription, what is the role of the TATA-binding protein (TBP)?
A. It recruits RNA Polymerase III to the mitochondrial genome
B. It recognizes and binds the TATA box to initiate the assembly of the pre-initiation
complex
C. It facilitates the phosphorylation of the CTD of RNA Pol II
D. It acts as a helicase to open the promoter region
Answer: B
Conceptual Explanation: TBP is a subunit of TFIID that recognizes the TATA box sequence
in the promoter, serving as a scaffold for other general transcription factors and RNA Pol II.
4. Which modification occurs at the 5’ end of a eukaryotic mRNA molecule shortly after
transcription begins?
A. Addition of a poly-A tail
B. Splicing of the first intron
, C. Addition of a 7-methylguanosine cap
D. Binding of the sigma factor
Answer: C
Conceptual Explanation: The 5’ cap (7-methylguanosine) is added to the nascent mRNA
transcript to protect it from degradation and assist in ribosome binding.
5. What is the primary function of the sigma factor in prokaryotic transcription?
A. Elongation of the RNA chain
B. Termination of transcription at rho-independent sites
C. Catalyzing the formation of phosphodiester bonds
D. Recognition of specific promoter sequences (-10 and -35 boxes)
Answer: D
Conceptual Explanation: The sigma factor is a subunit of the bacterial RNA polymerase
holoenzyme that ensures the enzyme binds specifically to promoter regions to initiate
transcription.
6. During translation, which site of the ribosome does the initiator tRNA-Met first enter?
A. A site
B. E site
C. P site
