BIOL 271 Module 3 Exam Practice Questions &
Answers (Verified Update)
This comprehensive study guide covers the core domains tested
on BIOL 271 Module 3: Microbial Genetics, DNA Replication,
Transcription & Translation at Portage Learning. It includes over
200 original practice questions with detailed rationales,
organized by the core exam domains: DNA Structure &
Replication, Transcription, Translation, Gene Regulation
(Operons), and Mutations & Gene Transfer.
Exam Overview & Blueprint:
Parameter Details
Exam Format LockDown Browser, multiple-choice, true/false, and short-answer questions
Module 3 Microbial genetics, DNA replication, transcription, translation, gene regulation, mutations,
Coverage horizontal gene transfer
DNA structure, semiconservative replication, enzymes of replication, transcription in
Core Topics prokaryotes, translation, lac/trp operons, mutation types,
conjugation/transformation/transduction
Scenario-based application questions, enzyme function identification, operon regulation lo
2026 Focus
mutation consequence prediction
,Section 1: DNA Structure & Replication
1.1 DNA Structure
Q1. A microbiology student is studying bacterial DNA replication
and observes that the two strands of the double helix run in
opposite directions. Which of the following correctly describes
this arrangement?
A) Parallel strands with 5′ to 3′ orientation on both strands
B) Antiparallel strands with one strand running 5′ to 3′ and the
other 3′ to 5′
C) Parallel strands with 3′ to 5′ orientation on both strands
D) Antiparallel strands with both strands running 5′ to 5′
Answer: B
Rationale: DNA strands are antiparallel, meaning one strand
runs 5′ to 3′ while the complementary strand runs 3′ to 5′. This
fundamental property is critical for DNA replication, as DNA
polymerase can only synthesize in the 5′ to 3′ direction. Options
A and C incorrectly describe the strands as parallel, and option
D misstates the orientation.
Q2. Which of the following best describes the semiconservative
model of DNA replication?
,A) Each daughter DNA molecule consists of two newly
synthesized strands
B) Each daughter DNA molecule consists of two parental strands
C) Each daughter DNA molecule consists of one parental strand
and one newly synthesized strand
D) DNA is synthesized in fragments that are later joined
randomly
Answer: C
Rationale: The semiconservative model states that each
daughter DNA molecule contains one original (parental) strand
and one newly synthesized strand. This was demonstrated by
the Meselson-Stahl experiment.
Q3. According to the central dogma of molecular biology, what
is the correct flow of genetic information in cells?
A) Protein → DNA → RNA
B) DNA → RNA → Protein
C) RNA → DNA → Protein
D) DNA → Protein → RNA
Answer: B
Rationale: The central dogma describes the flow of genetic
information as DNA → RNA → Protein. DNA is transcribed into
RNA, which is then translated into protein.
Q4. What is the name of the site where DNA replication begins
in bacteria?
, A) Telomere
B) Centromere
C) Origin of replication (oriC)
D) Promoter
Answer: C
Rationale: In bacteria, DNA replication initiates at a specific
sequence called the origin of replication (oriC). This is a single
site on the circular chromosome where replication begins.
Q5. What is the function of single-stranded binding protein
(SSB) in DNA replication?
A) To unwind the DNA double helix
B) To stabilize single-stranded DNA and prevent it from re-
annealing
C) To synthesize RNA primers
D) To remove RNA primers and replace them with DNA
Answer: B
Rationale: SSB proteins bind to single-stranded DNA during
replication to prevent the strands from re-annealing and to
protect them from degradation. They stabilize the replication
fork.
Q6. Which of the following is TRUE about bacterial DNA?
A) It is linear and found in the nucleus
B) It is circular and found in the nucleoid region
Answers (Verified Update)
This comprehensive study guide covers the core domains tested
on BIOL 271 Module 3: Microbial Genetics, DNA Replication,
Transcription & Translation at Portage Learning. It includes over
200 original practice questions with detailed rationales,
organized by the core exam domains: DNA Structure &
Replication, Transcription, Translation, Gene Regulation
(Operons), and Mutations & Gene Transfer.
Exam Overview & Blueprint:
Parameter Details
Exam Format LockDown Browser, multiple-choice, true/false, and short-answer questions
Module 3 Microbial genetics, DNA replication, transcription, translation, gene regulation, mutations,
Coverage horizontal gene transfer
DNA structure, semiconservative replication, enzymes of replication, transcription in
Core Topics prokaryotes, translation, lac/trp operons, mutation types,
conjugation/transformation/transduction
Scenario-based application questions, enzyme function identification, operon regulation lo
2026 Focus
mutation consequence prediction
,Section 1: DNA Structure & Replication
1.1 DNA Structure
Q1. A microbiology student is studying bacterial DNA replication
and observes that the two strands of the double helix run in
opposite directions. Which of the following correctly describes
this arrangement?
A) Parallel strands with 5′ to 3′ orientation on both strands
B) Antiparallel strands with one strand running 5′ to 3′ and the
other 3′ to 5′
C) Parallel strands with 3′ to 5′ orientation on both strands
D) Antiparallel strands with both strands running 5′ to 5′
Answer: B
Rationale: DNA strands are antiparallel, meaning one strand
runs 5′ to 3′ while the complementary strand runs 3′ to 5′. This
fundamental property is critical for DNA replication, as DNA
polymerase can only synthesize in the 5′ to 3′ direction. Options
A and C incorrectly describe the strands as parallel, and option
D misstates the orientation.
Q2. Which of the following best describes the semiconservative
model of DNA replication?
,A) Each daughter DNA molecule consists of two newly
synthesized strands
B) Each daughter DNA molecule consists of two parental strands
C) Each daughter DNA molecule consists of one parental strand
and one newly synthesized strand
D) DNA is synthesized in fragments that are later joined
randomly
Answer: C
Rationale: The semiconservative model states that each
daughter DNA molecule contains one original (parental) strand
and one newly synthesized strand. This was demonstrated by
the Meselson-Stahl experiment.
Q3. According to the central dogma of molecular biology, what
is the correct flow of genetic information in cells?
A) Protein → DNA → RNA
B) DNA → RNA → Protein
C) RNA → DNA → Protein
D) DNA → Protein → RNA
Answer: B
Rationale: The central dogma describes the flow of genetic
information as DNA → RNA → Protein. DNA is transcribed into
RNA, which is then translated into protein.
Q4. What is the name of the site where DNA replication begins
in bacteria?
, A) Telomere
B) Centromere
C) Origin of replication (oriC)
D) Promoter
Answer: C
Rationale: In bacteria, DNA replication initiates at a specific
sequence called the origin of replication (oriC). This is a single
site on the circular chromosome where replication begins.
Q5. What is the function of single-stranded binding protein
(SSB) in DNA replication?
A) To unwind the DNA double helix
B) To stabilize single-stranded DNA and prevent it from re-
annealing
C) To synthesize RNA primers
D) To remove RNA primers and replace them with DNA
Answer: B
Rationale: SSB proteins bind to single-stranded DNA during
replication to prevent the strands from re-annealing and to
protect them from degradation. They stabilize the replication
fork.
Q6. Which of the following is TRUE about bacterial DNA?
A) It is linear and found in the nucleus
B) It is circular and found in the nucleoid region
