1
BIOD 210 FINAL EXAM 2026/2027 | GENETICS –
PORTAGE LEARNING | EXPERT VERIFIED | 100
QUESTIONS & COMPLETE RATIONALES | PASS
GUARANTEED - A+ GRADED
SECTION 1: GENE REGULATION IN PROKARYOTES (Questions 1-15)
Q1: In prokaryotes, gene expression is primarily regulated at the level of:
A. Transcription
B. Translation
C. Post-translation
D. DNA replication
Correct Answer: A
Rationale: In prokaryotes, gene expression is primarily regulated at the level of transcription through
mechanisms such as operons, promoters, and transcription factors. This allows rapid response to
environmental changes. Regulation at translation (B), post-translation (C), and replication (D) occurs
but is not the primary level. Key teaching point: Prokaryotic gene regulation is primarily at the
transcriptional level, allowing rapid adaptation to environmental changes.
Q2: The lac operon in E. coli is an example of:
A. Positive regulation only
B. Negative regulation only
C. Both positive and negative regulation
D. No regulation
Correct Answer: C
Rationale: The lac operon is regulated by both positive regulation (CAP-cAMP complex enhances
transcription when glucose is low) and negative regulation (lac repressor inhibits transcription in the
absence of lactose). Key teaching point: The lac operon demonstrates both positive (CAP) and
negative (repressor) regulation mechanisms.
Q3: In the lac operon, the lac repressor binds to which region?
A. Promoter
B. Operator
C. Structural genes
D. Terminator
Correct Answer: B
,2
Rationale: The lac repressor binds to the operator region of the lac operon, preventing RNA
polymerase from transcribing the structural genes. When allolactose (inducer) binds to the
repressor, it changes shape and releases from the operator. Key teaching point: The lac repressor
binds to the operator to block transcription; allolactose induces transcription by inactivating the
repressor.
Q4: The trp operon is an example of:
A. Inducible operon
B. Repressible operon
C. Positive regulation
D. Constitutive expression
Correct Answer: B
Rationale: The trp operon is a repressible operon that is normally "on" and is repressed when
tryptophan is abundant. The trp repressor requires tryptophan as a co-repressor to bind to the
operator. The lac operon (A) is an inducible operon. Key teaching point: The trp operon is
repressible—tryptophan acts as a co-repressor to inhibit transcription when abundant.
Q5: The CAP-cAMP complex in the lac operon:
A. Represses transcription
B. Enhances transcription
C. Terminates transcription
D. Is not involved in regulation
Correct Answer: B
Rationale: The CAP-cAMP complex binds to the CAP site near the promoter and enhances
transcription of the lac operon when glucose is low. This is an example of positive regulation. Key
teaching point: CAP-cAMP enhances lac operon transcription when glucose is low—positive
regulation.
Q6: In the lac operon, the inducer molecule is:
A. Glucose
B. Lactose
C. Allolactose
D. Tryptophan
Correct Answer: C
Rationale: Allolactose is the inducer molecule that binds to the lac repressor and inactivates it,
allowing transcription of the lac operon. Lactose (B) is converted to allolactose, which serves as the
actual inducer. Key teaching point: Allolactose, not lactose, is the true inducer of the lac operon.
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Q7: The ara operon is regulated by:
A. Positive regulation only
B. Negative regulation only
C. Both positive and negative regulation
D. No regulation
Correct Answer: C
Rationale: The ara operon is regulated by both positive and negative regulation through the AraC
protein, which can act as both an activator and a repressor depending on the presence of
arabinose. Key teaching point: The ara operon uses AraC as both an activator and repressor—dual
regulation.
Q8: Catabolite repression refers to:
A. Repression of the lac operon when glucose is present
B. Repression of the trp operon when tryptophan is present
C. Activation of the lac operon when glucose is low
D. Repression of the ara operon when arabinose is present
Correct Answer: A
Rationale: Catabolite repression is the inhibition of the lac operon (and other catabolic operons)
when glucose is present. Glucose lowers cAMP levels, preventing CAP-cAMP from binding and
activating transcription. Key teaching point: Catabolite repression = glucose inhibits lac operon
expression by lowering cAMP levels.
Q9: The attenuation mechanism in the trp operon involves:
A. Premature termination of transcription
B. Binding of a repressor
C. Activation of transcription
D. Post-translational modification
Correct Answer: A
Rationale: Attenuation is a regulatory mechanism in the trp operon where transcription is
prematurely terminated (attenuated) when tryptophan is abundant. This occurs through the
formation of a hairpin structure in the mRNA that causes RNA polymerase to dissociate. Key
teaching point: Attenuation is premature transcription termination in the trp operon when
tryptophan is abundant.
Q10: Attenuation in the trp operon relies on:
A. The trp repressor
B. The CAP-cAMP complex
C. The leader sequence and coupled transcription-translation
D. The operator region
BIOD 210 FINAL EXAM 2026/2027 | GENETICS –
PORTAGE LEARNING | EXPERT VERIFIED | 100
QUESTIONS & COMPLETE RATIONALES | PASS
GUARANTEED - A+ GRADED
SECTION 1: GENE REGULATION IN PROKARYOTES (Questions 1-15)
Q1: In prokaryotes, gene expression is primarily regulated at the level of:
A. Transcription
B. Translation
C. Post-translation
D. DNA replication
Correct Answer: A
Rationale: In prokaryotes, gene expression is primarily regulated at the level of transcription through
mechanisms such as operons, promoters, and transcription factors. This allows rapid response to
environmental changes. Regulation at translation (B), post-translation (C), and replication (D) occurs
but is not the primary level. Key teaching point: Prokaryotic gene regulation is primarily at the
transcriptional level, allowing rapid adaptation to environmental changes.
Q2: The lac operon in E. coli is an example of:
A. Positive regulation only
B. Negative regulation only
C. Both positive and negative regulation
D. No regulation
Correct Answer: C
Rationale: The lac operon is regulated by both positive regulation (CAP-cAMP complex enhances
transcription when glucose is low) and negative regulation (lac repressor inhibits transcription in the
absence of lactose). Key teaching point: The lac operon demonstrates both positive (CAP) and
negative (repressor) regulation mechanisms.
Q3: In the lac operon, the lac repressor binds to which region?
A. Promoter
B. Operator
C. Structural genes
D. Terminator
Correct Answer: B
,2
Rationale: The lac repressor binds to the operator region of the lac operon, preventing RNA
polymerase from transcribing the structural genes. When allolactose (inducer) binds to the
repressor, it changes shape and releases from the operator. Key teaching point: The lac repressor
binds to the operator to block transcription; allolactose induces transcription by inactivating the
repressor.
Q4: The trp operon is an example of:
A. Inducible operon
B. Repressible operon
C. Positive regulation
D. Constitutive expression
Correct Answer: B
Rationale: The trp operon is a repressible operon that is normally "on" and is repressed when
tryptophan is abundant. The trp repressor requires tryptophan as a co-repressor to bind to the
operator. The lac operon (A) is an inducible operon. Key teaching point: The trp operon is
repressible—tryptophan acts as a co-repressor to inhibit transcription when abundant.
Q5: The CAP-cAMP complex in the lac operon:
A. Represses transcription
B. Enhances transcription
C. Terminates transcription
D. Is not involved in regulation
Correct Answer: B
Rationale: The CAP-cAMP complex binds to the CAP site near the promoter and enhances
transcription of the lac operon when glucose is low. This is an example of positive regulation. Key
teaching point: CAP-cAMP enhances lac operon transcription when glucose is low—positive
regulation.
Q6: In the lac operon, the inducer molecule is:
A. Glucose
B. Lactose
C. Allolactose
D. Tryptophan
Correct Answer: C
Rationale: Allolactose is the inducer molecule that binds to the lac repressor and inactivates it,
allowing transcription of the lac operon. Lactose (B) is converted to allolactose, which serves as the
actual inducer. Key teaching point: Allolactose, not lactose, is the true inducer of the lac operon.
, 3
Q7: The ara operon is regulated by:
A. Positive regulation only
B. Negative regulation only
C. Both positive and negative regulation
D. No regulation
Correct Answer: C
Rationale: The ara operon is regulated by both positive and negative regulation through the AraC
protein, which can act as both an activator and a repressor depending on the presence of
arabinose. Key teaching point: The ara operon uses AraC as both an activator and repressor—dual
regulation.
Q8: Catabolite repression refers to:
A. Repression of the lac operon when glucose is present
B. Repression of the trp operon when tryptophan is present
C. Activation of the lac operon when glucose is low
D. Repression of the ara operon when arabinose is present
Correct Answer: A
Rationale: Catabolite repression is the inhibition of the lac operon (and other catabolic operons)
when glucose is present. Glucose lowers cAMP levels, preventing CAP-cAMP from binding and
activating transcription. Key teaching point: Catabolite repression = glucose inhibits lac operon
expression by lowering cAMP levels.
Q9: The attenuation mechanism in the trp operon involves:
A. Premature termination of transcription
B. Binding of a repressor
C. Activation of transcription
D. Post-translational modification
Correct Answer: A
Rationale: Attenuation is a regulatory mechanism in the trp operon where transcription is
prematurely terminated (attenuated) when tryptophan is abundant. This occurs through the
formation of a hairpin structure in the mRNA that causes RNA polymerase to dissociate. Key
teaching point: Attenuation is premature transcription termination in the trp operon when
tryptophan is abundant.
Q10: Attenuation in the trp operon relies on:
A. The trp repressor
B. The CAP-cAMP complex
C. The leader sequence and coupled transcription-translation
D. The operator region
