MICROBIOLOGY MODULE 4 EXAM:
MICROBIAL GENETICS AND
BIOTECHNOLOGY
1. Which enzyme is responsible for synthesizing a short RNA primer to provide a 3’-OH group
for DNA polymerase to begin replication?
A. DNA Ligase
B. Primase
C. DNA Polymerase I
D. Helicase
Answer: B
Conceptual Explanation: Primase is an RNA polymerase that creates a short RNA primer,
which is essential because DNA polymerase can only add nucleotides to an existing 3’-OH
group.
2. In DNA replication, the leading strand is synthesized continuously, while the lagging strand
is synthesized in fragments called:
A. Griffith fragments
B. Chargaff units
,C. Okazaki fragments
D. Watson-Crick sequences
Answer: C
Conceptual Explanation: Due to the antiparallel nature of DNA and the fact that DNA
polymerase only works in the 5’ to 3’ direction, the lagging strand is built in short segments
known as Okazaki fragments.
3. What is the function of DNA Gyrase (Topoisomerase II) during replication?
A. It proofreads the newly synthesized DNA strand.
B. It stabilizes single-stranded DNA to prevent re-annealing.
C. It seals the nicks between DNA fragments.
D. It relieves torsional strain and supercoiling ahead of the replication fork.
Answer: D
Conceptual Explanation: DNA Gyrase travels ahead of the replication fork to relieve the
tension caused by the unwinding of the double helix.
4. Which of the following is characteristic of the bacterial chromosome but NOT usually found
in eukaryotic chromosomes?
A. It is linear.
B. It is typically a single circular molecule.
C. It is associated with histone proteins.
, D. It contains multiple origins of replication.
Answer: B
Conceptual Explanation: Bacterial chromosomes are generally circular and localized in
the nucleoid, whereas eukaryotic chromosomes are linear and found in the nucleus.
5. Which enzyme removes the RNA primers and replaces them with DNA nucleotides during
replication?
A. DNA Polymerase I
B. DNA Polymerase III
C. Exonuclease
D. RNA Polymerase
Answer: A
Conceptual Explanation: DNA Polymerase I has 5’ to 3’ exonuclease activity, allowing it to
remove RNA primers and replace them with DNA.
6. During transcription, the region of DNA where RNA polymerase binds to initiate the
process is called the:
A. Operator
B. Promoter
C. Exon
D. Intron
MICROBIAL GENETICS AND
BIOTECHNOLOGY
1. Which enzyme is responsible for synthesizing a short RNA primer to provide a 3’-OH group
for DNA polymerase to begin replication?
A. DNA Ligase
B. Primase
C. DNA Polymerase I
D. Helicase
Answer: B
Conceptual Explanation: Primase is an RNA polymerase that creates a short RNA primer,
which is essential because DNA polymerase can only add nucleotides to an existing 3’-OH
group.
2. In DNA replication, the leading strand is synthesized continuously, while the lagging strand
is synthesized in fragments called:
A. Griffith fragments
B. Chargaff units
,C. Okazaki fragments
D. Watson-Crick sequences
Answer: C
Conceptual Explanation: Due to the antiparallel nature of DNA and the fact that DNA
polymerase only works in the 5’ to 3’ direction, the lagging strand is built in short segments
known as Okazaki fragments.
3. What is the function of DNA Gyrase (Topoisomerase II) during replication?
A. It proofreads the newly synthesized DNA strand.
B. It stabilizes single-stranded DNA to prevent re-annealing.
C. It seals the nicks between DNA fragments.
D. It relieves torsional strain and supercoiling ahead of the replication fork.
Answer: D
Conceptual Explanation: DNA Gyrase travels ahead of the replication fork to relieve the
tension caused by the unwinding of the double helix.
4. Which of the following is characteristic of the bacterial chromosome but NOT usually found
in eukaryotic chromosomes?
A. It is linear.
B. It is typically a single circular molecule.
C. It is associated with histone proteins.
, D. It contains multiple origins of replication.
Answer: B
Conceptual Explanation: Bacterial chromosomes are generally circular and localized in
the nucleoid, whereas eukaryotic chromosomes are linear and found in the nucleus.
5. Which enzyme removes the RNA primers and replaces them with DNA nucleotides during
replication?
A. DNA Polymerase I
B. DNA Polymerase III
C. Exonuclease
D. RNA Polymerase
Answer: A
Conceptual Explanation: DNA Polymerase I has 5’ to 3’ exonuclease activity, allowing it to
remove RNA primers and replace them with DNA.
6. During transcription, the region of DNA where RNA polymerase binds to initiate the
process is called the:
A. Operator
B. Promoter
C. Exon
D. Intron
