BIOL 351 / BIOL351 Module 1 Exam Actual 2026/2027
with Detailed Rationales | Complete Exam-Style
Questions | Pass Guaranteed – A+ Graded
SECTION 1: MOLECULAR BIOLOGY & GENETICS (Q1–Q12)
Q1: During DNA replication in eukaryotes, which enzyme is primarily responsible for
synthesizing the leading strand continuously?
A. DNA ligase
B. DNA polymerase α
C. DNA polymerase δ
D. Primase
Correct Answer: C
Rationale: Correct because DNA polymerase δ is the main enzyme responsible for
continuous synthesis of the leading strand and extension of Okazaki fragments on
the lagging strand in eukaryotes.
Q2: In the proofreading function of DNA replication, which activity allows DNA
polymerase to remove an incorrectly paired nucleotide immediately after
incorporation?
A. 5' → 3' exonuclease activity
B. Endonuclease activity
C. 3' → 5' exonuclease activity
D. Helicase activity
Correct Answer: C
Rationale: Correct because the 3' → 5' exonuclease activity of DNA polymerase
allows it to back up and remove mismatched nucleotides from the 3' end before
continuing synthesis.
Q3: What is the primary function of Okazaki fragments during DNA replication?
A. To seal nicks between DNA segments
B. To synthesize the leading strand continuously
C. To synthesize the lagging strand discontinuously
D. To unwind the DNA double helix
Correct Answer: C
, Rationale: Correct because Okazaki fragments are short DNA segments synthesized
discontinuously on the lagging strand template, which are later joined by DNA ligase.
Q4: Which DNA repair mechanism specifically recognizes and corrects base-pair
mismatches that escape proofreading during replication?
A. Base excision repair
B. Nucleotide excision repair
C. Mismatch repair
D. Homologous recombination repair
Correct Answer: C
Rationale: Correct because mismatch repair recognizes distortions in the DNA helix
caused by mispaired bases and excises the incorrect segment using the parental
strand as a template.
Q5: During homologous recombination in meiosis, which protein catalyzes the
invasion of the single-stranded DNA into the homologous duplex?
A. DNA ligase
B. Topoisomerase
C. Rad51 (RecA in bacteria)
D. DNA polymerase I
Correct Answer: C
Rationale: Correct because Rad51 (and its bacterial homolog RecA) mediates strand
invasion and pairing between homologous DNA sequences during recombination.
Q6: What is the primary role of telomerase in eukaryotic cells?
A. To repair double-strand breaks
B. To unwind DNA at the replication fork
C. To extend telomere repeats at chromosome ends
D. To degrade RNA primers
Correct Answer: C
Rationale: Correct because telomerase is a reverse transcriptase that adds repetitive
DNA sequences to the ends of chromosomes, compensating for the end-replication
problem.
Q7: In eukaryotic transcription, which factor recognizes the TATA box and recruits
RNA polymerase II to the promoter?
A. TFIIH
B. TFIIE
C. TFIID
with Detailed Rationales | Complete Exam-Style
Questions | Pass Guaranteed – A+ Graded
SECTION 1: MOLECULAR BIOLOGY & GENETICS (Q1–Q12)
Q1: During DNA replication in eukaryotes, which enzyme is primarily responsible for
synthesizing the leading strand continuously?
A. DNA ligase
B. DNA polymerase α
C. DNA polymerase δ
D. Primase
Correct Answer: C
Rationale: Correct because DNA polymerase δ is the main enzyme responsible for
continuous synthesis of the leading strand and extension of Okazaki fragments on
the lagging strand in eukaryotes.
Q2: In the proofreading function of DNA replication, which activity allows DNA
polymerase to remove an incorrectly paired nucleotide immediately after
incorporation?
A. 5' → 3' exonuclease activity
B. Endonuclease activity
C. 3' → 5' exonuclease activity
D. Helicase activity
Correct Answer: C
Rationale: Correct because the 3' → 5' exonuclease activity of DNA polymerase
allows it to back up and remove mismatched nucleotides from the 3' end before
continuing synthesis.
Q3: What is the primary function of Okazaki fragments during DNA replication?
A. To seal nicks between DNA segments
B. To synthesize the leading strand continuously
C. To synthesize the lagging strand discontinuously
D. To unwind the DNA double helix
Correct Answer: C
, Rationale: Correct because Okazaki fragments are short DNA segments synthesized
discontinuously on the lagging strand template, which are later joined by DNA ligase.
Q4: Which DNA repair mechanism specifically recognizes and corrects base-pair
mismatches that escape proofreading during replication?
A. Base excision repair
B. Nucleotide excision repair
C. Mismatch repair
D. Homologous recombination repair
Correct Answer: C
Rationale: Correct because mismatch repair recognizes distortions in the DNA helix
caused by mispaired bases and excises the incorrect segment using the parental
strand as a template.
Q5: During homologous recombination in meiosis, which protein catalyzes the
invasion of the single-stranded DNA into the homologous duplex?
A. DNA ligase
B. Topoisomerase
C. Rad51 (RecA in bacteria)
D. DNA polymerase I
Correct Answer: C
Rationale: Correct because Rad51 (and its bacterial homolog RecA) mediates strand
invasion and pairing between homologous DNA sequences during recombination.
Q6: What is the primary role of telomerase in eukaryotic cells?
A. To repair double-strand breaks
B. To unwind DNA at the replication fork
C. To extend telomere repeats at chromosome ends
D. To degrade RNA primers
Correct Answer: C
Rationale: Correct because telomerase is a reverse transcriptase that adds repetitive
DNA sequences to the ends of chromosomes, compensating for the end-replication
problem.
Q7: In eukaryotic transcription, which factor recognizes the TATA box and recruits
RNA polymerase II to the promoter?
A. TFIIH
B. TFIIE
C. TFIID
