BIOD 101 MODULE 6: GENETICS AND
MOLECULAR BIOLOGY QUESTIONS &
VERIFIED ANSWERS (A+ GUARANTEE)
1. Which of the following describes the correct orientation of DNA strands in a double helix?
A. Antiparallel 5’ to 3’ and 3’ to 5’
B. Parallel 3’ to 5’
C. Parallel 5’ to 3’
D. Randomly oriented strands
Answer: A
Conceptual Explanation: DNA strands are antiparallel, meaning one strand runs 5’ to 3’
while the other runs 3’ to 5’, allowing for hydrogen bonding between complementary
bases.
2. According to Chargaff’s rules, if a DNA sample contains 20% Guanine, what is the
percentage of Adenine?
A. 30%
B. 80%
C. 20%
D. 60%
,Answer: A
Conceptual Explanation: If G is 20%, then C is also 20% (Total G+C = 40%). The
remaining 60% must be split equally between A and T, so A is 30%.
3. Which enzyme is responsible for unwinding the DNA double helix during replication?
A. DNA Polymerase III
B. Ligase
C. Helicase
D. Topoisomerase
Answer: C
Conceptual Explanation: Helicase breaks the hydrogen bonds between nitrogenous bases
to separate the two strands and create the replication fork.
4. What is the primary function of DNA Polymerase III in prokaryotes?
A. Unzipping the double helix
B. Removing RNA primers
C. Repairing damaged DNA segments
D. Synthesizing new DNA in the 5’ to 3’ direction
Answer: D
, Conceptual Explanation: DNA Polymerase III is the main enzyme that adds nucleotides to
the growing DNA strand in the 5’ to 3’ direction.
5. In DNA replication, why is the lagging strand synthesized in Okazaki fragments?
A. Because the lagging strand is shorter than the leading strand
B. Because DNA Polymerase can only work in the 5’ to 3’ direction
C. Because RNA primers cannot bind to the lagging strand
D. Because helicase only unwinds one strand at a time
Answer: B
Conceptual Explanation: Since DNA strands are antiparallel and polymerase only adds to
the 3’ end, the strand opening in the opposite direction must be made in short segments.
6. Which enzyme facilitates the joining of Okazaki fragments?
A. DNA Ligase
B. Primase
C. DNA Polymerase I
D. Helicase
Answer: A
Conceptual Explanation: DNA Ligase acts as a molecular glue, forming phosphodiester
bonds between the sugar-phosphate backbones of DNA fragments.
MOLECULAR BIOLOGY QUESTIONS &
VERIFIED ANSWERS (A+ GUARANTEE)
1. Which of the following describes the correct orientation of DNA strands in a double helix?
A. Antiparallel 5’ to 3’ and 3’ to 5’
B. Parallel 3’ to 5’
C. Parallel 5’ to 3’
D. Randomly oriented strands
Answer: A
Conceptual Explanation: DNA strands are antiparallel, meaning one strand runs 5’ to 3’
while the other runs 3’ to 5’, allowing for hydrogen bonding between complementary
bases.
2. According to Chargaff’s rules, if a DNA sample contains 20% Guanine, what is the
percentage of Adenine?
A. 30%
B. 80%
C. 20%
D. 60%
,Answer: A
Conceptual Explanation: If G is 20%, then C is also 20% (Total G+C = 40%). The
remaining 60% must be split equally between A and T, so A is 30%.
3. Which enzyme is responsible for unwinding the DNA double helix during replication?
A. DNA Polymerase III
B. Ligase
C. Helicase
D. Topoisomerase
Answer: C
Conceptual Explanation: Helicase breaks the hydrogen bonds between nitrogenous bases
to separate the two strands and create the replication fork.
4. What is the primary function of DNA Polymerase III in prokaryotes?
A. Unzipping the double helix
B. Removing RNA primers
C. Repairing damaged DNA segments
D. Synthesizing new DNA in the 5’ to 3’ direction
Answer: D
, Conceptual Explanation: DNA Polymerase III is the main enzyme that adds nucleotides to
the growing DNA strand in the 5’ to 3’ direction.
5. In DNA replication, why is the lagging strand synthesized in Okazaki fragments?
A. Because the lagging strand is shorter than the leading strand
B. Because DNA Polymerase can only work in the 5’ to 3’ direction
C. Because RNA primers cannot bind to the lagging strand
D. Because helicase only unwinds one strand at a time
Answer: B
Conceptual Explanation: Since DNA strands are antiparallel and polymerase only adds to
the 3’ end, the strand opening in the opposite direction must be made in short segments.
6. Which enzyme facilitates the joining of Okazaki fragments?
A. DNA Ligase
B. Primase
C. DNA Polymerase I
D. Helicase
Answer: A
Conceptual Explanation: DNA Ligase acts as a molecular glue, forming phosphodiester
bonds between the sugar-phosphate backbones of DNA fragments.
