1
BIOL 1009 - MIDTERM EXAM 2 2026/2027 | 50
VERIFIED Q&A | DETAILED RATIONALES | NGN-
ALIGNED | PASS GUARANTEED – A+ GRADED
SECTION I: DNA REPLICATION AND REPAIR - Questions 1-10
Q1: DNA replication overview
The student is reviewing DNA replication. What is the purpose of DNA replication?
A. To produce proteins
B. To produce identical copies of DNA
C. To produce RNA
D. To produce gametes
Correct Answer: B
Rationale: DNA replication produces two identical copies of the original DNA molecule. This is
essential for cell division, ensuring each daughter cell receives a complete set of genetic information.
Protein production is translation, RNA production is transcription, and gamete production involves
meiosis. [100% CORRECT]
Q2: Semiconservative replication
The student is reviewing DNA replication models. What does semiconservative replication mean?
A. Both strands of DNA are completely new
B. One strand is conserved and one is new in each daughter molecule
C. Both original strands remain together
D. DNA is replicated conservatively
Correct Answer: B
Rationale: Semiconservative replication means each new DNA molecule consists of one original
(conserved) strand and one newly synthesized strand. This was demonstrated by the Meselson-Stahl
experiment using nitrogen isotopes. [100% CORRECT]
Q3: Helicase function
The student is reviewing replication enzymes. What is the function of helicase during DNA
replication?
A. To synthesize new DNA strands
B. To unwind the DNA double helix
C. To proofread DNA
D. To join DNA fragments
Correct Answer: B
Rationale: Helicase unwinds and separates the two strands of the DNA double helix at the
, 2
replication fork, creating single-stranded templates for replication. DNA polymerase synthesizes new
strands, and ligase joins fragments. [100% CORRECT]
Q4: DNA polymerase direction
The student is reviewing DNA synthesis. In which direction does DNA polymerase synthesize new
strands?
A. 3' to 5'
B. 5' to 3'
C. Both directions
D. Randomly
Correct Answer: B
Rationale: DNA polymerase synthesizes new DNA strands in the 5' to 3' direction only. This means
the leading strand is synthesized continuously, while the lagging strand is synthesized in Okazaki
fragments discontinuously. [100% CORRECT]
Q5: Okazaki fragments
The student is reviewing lagging strand synthesis. What are Okazaki fragments?
A. Short DNA segments on the leading strand
B. Short DNA segments on the lagging strand
C. RNA primers
D. Proteins that stabilize DNA
Correct Answer: B
Rationale: Okazaki fragments are short DNA segments synthesized discontinuously on the lagging
strand. They are later joined together by DNA ligase to form a continuous strand. [100% CORRECT]
Q6: DNA ligase
The student is reviewing replication enzymes. What is the role of DNA ligase?
A. To unwind DNA
B. To synthesize RNA primers
C. To join Okazaki fragments
D. To proofread DNA
Correct Answer: C
Rationale: DNA ligase joins Okazaki fragments on the lagging strand by forming phosphodiester
bonds between adjacent nucleotides, creating a continuous DNA strand. [100% CORRECT]
Q7: RNA primer
The student is reviewing replication initiation. Why is an RNA primer required for DNA replication?
A. DNA polymerase can only add nucleotides to an existing strand
B. RNA is more stable than DNA
C. RNA primers provide energy
D. RNA primers proofread DNA
BIOL 1009 - MIDTERM EXAM 2 2026/2027 | 50
VERIFIED Q&A | DETAILED RATIONALES | NGN-
ALIGNED | PASS GUARANTEED – A+ GRADED
SECTION I: DNA REPLICATION AND REPAIR - Questions 1-10
Q1: DNA replication overview
The student is reviewing DNA replication. What is the purpose of DNA replication?
A. To produce proteins
B. To produce identical copies of DNA
C. To produce RNA
D. To produce gametes
Correct Answer: B
Rationale: DNA replication produces two identical copies of the original DNA molecule. This is
essential for cell division, ensuring each daughter cell receives a complete set of genetic information.
Protein production is translation, RNA production is transcription, and gamete production involves
meiosis. [100% CORRECT]
Q2: Semiconservative replication
The student is reviewing DNA replication models. What does semiconservative replication mean?
A. Both strands of DNA are completely new
B. One strand is conserved and one is new in each daughter molecule
C. Both original strands remain together
D. DNA is replicated conservatively
Correct Answer: B
Rationale: Semiconservative replication means each new DNA molecule consists of one original
(conserved) strand and one newly synthesized strand. This was demonstrated by the Meselson-Stahl
experiment using nitrogen isotopes. [100% CORRECT]
Q3: Helicase function
The student is reviewing replication enzymes. What is the function of helicase during DNA
replication?
A. To synthesize new DNA strands
B. To unwind the DNA double helix
C. To proofread DNA
D. To join DNA fragments
Correct Answer: B
Rationale: Helicase unwinds and separates the two strands of the DNA double helix at the
, 2
replication fork, creating single-stranded templates for replication. DNA polymerase synthesizes new
strands, and ligase joins fragments. [100% CORRECT]
Q4: DNA polymerase direction
The student is reviewing DNA synthesis. In which direction does DNA polymerase synthesize new
strands?
A. 3' to 5'
B. 5' to 3'
C. Both directions
D. Randomly
Correct Answer: B
Rationale: DNA polymerase synthesizes new DNA strands in the 5' to 3' direction only. This means
the leading strand is synthesized continuously, while the lagging strand is synthesized in Okazaki
fragments discontinuously. [100% CORRECT]
Q5: Okazaki fragments
The student is reviewing lagging strand synthesis. What are Okazaki fragments?
A. Short DNA segments on the leading strand
B. Short DNA segments on the lagging strand
C. RNA primers
D. Proteins that stabilize DNA
Correct Answer: B
Rationale: Okazaki fragments are short DNA segments synthesized discontinuously on the lagging
strand. They are later joined together by DNA ligase to form a continuous strand. [100% CORRECT]
Q6: DNA ligase
The student is reviewing replication enzymes. What is the role of DNA ligase?
A. To unwind DNA
B. To synthesize RNA primers
C. To join Okazaki fragments
D. To proofread DNA
Correct Answer: C
Rationale: DNA ligase joins Okazaki fragments on the lagging strand by forming phosphodiester
bonds between adjacent nucleotides, creating a continuous DNA strand. [100% CORRECT]
Q7: RNA primer
The student is reviewing replication initiation. Why is an RNA primer required for DNA replication?
A. DNA polymerase can only add nucleotides to an existing strand
B. RNA is more stable than DNA
C. RNA primers provide energy
D. RNA primers proofread DNA
