BIOD 102 Essential Biology II with Laboratory
Comprehensive Final Examination Actual Exam
2026/2027 | Detailed Rationales | Graded A+ Pass
Guaranteed
Q1: During DNA replication, which enzyme is responsible for synthesizing short RNA primers on
the lagging strand?
A. DNA polymerase III
B. Helicase
C. Primase [CORRECT]
D. Ligase
Correct Answer: C
Rationale: Correct because primase is the RNA polymerase that synthesizes the short RNA
primers required to initiate DNA synthesis on the lagging strand. This matches the standard
DNA replication mechanism in all living cells.
Q2: Which nitrogenous base is found exclusively in RNA and not in DNA?
A. Adenine
B. Uracil [CORRECT]
C. Thymine
D. Cytosine
Correct Answer: B
Rationale: Correct because uracil replaces thymine in RNA, pairing with adenine during
transcription and translation processes. This matches the fundamental structural difference
between RNA and DNA nucleotides.
Q3: In the process of transcription, which region of a gene serves as the binding site for RNA
polymerase to initiate synthesis?
A. Terminator sequence
B. Promoter [CORRECT]
C. Intron region
D. Poly-A tail
Correct Answer: B
Rationale: Correct because the promoter region contains specific DNA sequences recognized
by RNA polymerase and transcription factors, enabling proper initiation of transcription. This
matches the regulatory architecture of prokaryotic and eukaryotic genes.
Q4: A researcher observes that a bacterial operon is continuously expressed regardless of
environmental conditions. Which regulatory component is most likely defective?
A. Structural genes
B. Operator
C. Repressor protein [CORRECT]
,D. RNA polymerase
Correct Answer: C
Rationale: Correct because a nonfunctional repressor protein cannot bind the operator to block
transcription, resulting in constitutive expression of the operon. This matches the negative
inducible control mechanism observed in the lac operon model.
Q5: Which post-transcriptional modification is added to the 3' end of eukaryotic pre-mRNA to
protect it from degradation and facilitate export from the nucleus?
A. 5' cap
B. Spliceosome complex
C. Poly-A tail [CORRECT]
D. Intron excision
Correct Answer: C
Rationale: Correct because the poly-A tail consists of approximately 200 adenine nucleotides
added to the 3' end, stabilizing the mRNA and promoting translation initiation. This matches
standard eukaryotic mRNA processing protocols.
Q6: During translation, which molecule carries amino acids to the ribosome and contains an
anticodon complementary to the mRNA codon?
A. mRNA
B. rRNA
C. tRNA [CORRECT]
D. snRNA
Correct Answer: C
Rationale: Correct because transfer RNA (tRNA) functions as the adapter molecule, with each
tRNA carrying a specific amino acid and displaying an anticodon that base-pairs with the
corresponding mRNA codon. This matches the central dogma of molecular biology.
Q7: A laboratory technician performs a microarray analysis comparing cancer cells to normal
cells. The technician observes a red spot indicating high expression of a proto-oncogene. What
does this result indicate?
A. The gene is deleted in cancer cells
B. The gene is overexpressed in cancer cells [CORRECT]
C. The gene is methylated in normal cells
D. The gene is not transcribed in either cell type
Correct Answer: B
Rationale: Correct because in microarray analysis, red fluorescence typically indicates high
expression in the experimental sample (cancer cells) relative to the control, suggesting
upregulation of the proto-oncogene. This matches standard microarray interpretation where red
indicates increased expression.
Q8: Which enzyme proofreads newly synthesized DNA and removes mismatched nucleosomes
during replication?
A. DNA polymerase I
B. DNA polymerase III with 3'→5' exonuclease activity [CORRECT]
C. Topoisomerase
D. Telomerase
Correct Answer: B
, Rationale: Correct because DNA polymerase III possesses 3'→5' exonuclease activity, enabling
it to recognize and remove incorrectly paired nucleotides before continuing synthesis. This
matches the fidelity mechanism that maintains genomic stability during replication.
Q9: In eukaryotic gene expression, which of the following processes occurs exclusively in the
nucleus?
A. Translation
B. Transcription and RNA splicing [CORRECT]
C. Protein folding
D. Post-translational modification
Correct Answer: B
Rationale: Correct because transcription and pre-mRNA splicing are nuclear processes in
eukaryotes, while translation and subsequent protein modifications occur in the cytoplasm or
endomembrane system. This matches the compartmentalization of gene expression in
eukaryotic cells.
Q10: A scientist introduces a mutation in the TATA box of a eukaryotic gene. What is the most
likely consequence?
A. Increased translation efficiency
B. Decreased or absent transcription initiation [CORRECT]
C. Enhanced mRNA stability
D. Altered protein folding
Correct Answer: B
Rationale: Correct because the TATA box is a core promoter element recognized by
transcription factors and RNA polymerase II; mutations in this region typically impair
transcription initiation. This matches the essential role of promoter elements in eukaryotic gene
regulation.
Q11: Which of the following best describes the function of ribosomes in protein synthesis?
A. They store genetic information
B. They catalyze peptide bond formation between amino acids [CORRECT]
C. They transport proteins to the Golgi apparatus
D. They replicate DNA during cell division
Correct Answer: B
Rationale: Correct because the ribosomal RNA (rRNA) within the large ribosomal subunit
possesses peptidyl transferase activity, catalyzing the formation of peptide bonds during
translation. This matches the catalytic function of ribozymes in protein synthesis.
Q12: In the central dogma of molecular biology, information flows in which direction under
normal cellular conditions?
A. Protein → RNA → DNA
B. DNA → RNA → Protein [CORRECT]
C. RNA → DNA → Protein
D. Lipid → Carbohydrate → Protein
Correct Answer: B
Rationale: Correct because the central dogma describes the unidirectional flow of genetic
information from DNA through transcription to RNA, and through translation to functional
proteins. This matches the fundamental paradigm established by molecular biology research.
BIOD 102 Essential Biology II with Laboratory
Comprehensive Final Examination Actual Exam
2026/2027 | Detailed Rationales | Graded A+ Pass
Guaranteed
Q1: During DNA replication, which enzyme is responsible for synthesizing short RNA primers on
the lagging strand?
A. DNA polymerase III
B. Helicase
C. Primase [CORRECT]
D. Ligase
Correct Answer: C
Rationale: Correct because primase is the RNA polymerase that synthesizes the short RNA
primers required to initiate DNA synthesis on the lagging strand. This matches the standard
DNA replication mechanism in all living cells.
Q2: Which nitrogenous base is found exclusively in RNA and not in DNA?
A. Adenine
B. Uracil [CORRECT]
C. Thymine
D. Cytosine
Correct Answer: B
Rationale: Correct because uracil replaces thymine in RNA, pairing with adenine during
transcription and translation processes. This matches the fundamental structural difference
between RNA and DNA nucleotides.
Q3: In the process of transcription, which region of a gene serves as the binding site for RNA
polymerase to initiate synthesis?
A. Terminator sequence
B. Promoter [CORRECT]
C. Intron region
D. Poly-A tail
Correct Answer: B
Rationale: Correct because the promoter region contains specific DNA sequences recognized
by RNA polymerase and transcription factors, enabling proper initiation of transcription. This
matches the regulatory architecture of prokaryotic and eukaryotic genes.
Q4: A researcher observes that a bacterial operon is continuously expressed regardless of
environmental conditions. Which regulatory component is most likely defective?
A. Structural genes
B. Operator
C. Repressor protein [CORRECT]
,D. RNA polymerase
Correct Answer: C
Rationale: Correct because a nonfunctional repressor protein cannot bind the operator to block
transcription, resulting in constitutive expression of the operon. This matches the negative
inducible control mechanism observed in the lac operon model.
Q5: Which post-transcriptional modification is added to the 3' end of eukaryotic pre-mRNA to
protect it from degradation and facilitate export from the nucleus?
A. 5' cap
B. Spliceosome complex
C. Poly-A tail [CORRECT]
D. Intron excision
Correct Answer: C
Rationale: Correct because the poly-A tail consists of approximately 200 adenine nucleotides
added to the 3' end, stabilizing the mRNA and promoting translation initiation. This matches
standard eukaryotic mRNA processing protocols.
Q6: During translation, which molecule carries amino acids to the ribosome and contains an
anticodon complementary to the mRNA codon?
A. mRNA
B. rRNA
C. tRNA [CORRECT]
D. snRNA
Correct Answer: C
Rationale: Correct because transfer RNA (tRNA) functions as the adapter molecule, with each
tRNA carrying a specific amino acid and displaying an anticodon that base-pairs with the
corresponding mRNA codon. This matches the central dogma of molecular biology.
Q7: A laboratory technician performs a microarray analysis comparing cancer cells to normal
cells. The technician observes a red spot indicating high expression of a proto-oncogene. What
does this result indicate?
A. The gene is deleted in cancer cells
B. The gene is overexpressed in cancer cells [CORRECT]
C. The gene is methylated in normal cells
D. The gene is not transcribed in either cell type
Correct Answer: B
Rationale: Correct because in microarray analysis, red fluorescence typically indicates high
expression in the experimental sample (cancer cells) relative to the control, suggesting
upregulation of the proto-oncogene. This matches standard microarray interpretation where red
indicates increased expression.
Q8: Which enzyme proofreads newly synthesized DNA and removes mismatched nucleosomes
during replication?
A. DNA polymerase I
B. DNA polymerase III with 3'→5' exonuclease activity [CORRECT]
C. Topoisomerase
D. Telomerase
Correct Answer: B
, Rationale: Correct because DNA polymerase III possesses 3'→5' exonuclease activity, enabling
it to recognize and remove incorrectly paired nucleotides before continuing synthesis. This
matches the fidelity mechanism that maintains genomic stability during replication.
Q9: In eukaryotic gene expression, which of the following processes occurs exclusively in the
nucleus?
A. Translation
B. Transcription and RNA splicing [CORRECT]
C. Protein folding
D. Post-translational modification
Correct Answer: B
Rationale: Correct because transcription and pre-mRNA splicing are nuclear processes in
eukaryotes, while translation and subsequent protein modifications occur in the cytoplasm or
endomembrane system. This matches the compartmentalization of gene expression in
eukaryotic cells.
Q10: A scientist introduces a mutation in the TATA box of a eukaryotic gene. What is the most
likely consequence?
A. Increased translation efficiency
B. Decreased or absent transcription initiation [CORRECT]
C. Enhanced mRNA stability
D. Altered protein folding
Correct Answer: B
Rationale: Correct because the TATA box is a core promoter element recognized by
transcription factors and RNA polymerase II; mutations in this region typically impair
transcription initiation. This matches the essential role of promoter elements in eukaryotic gene
regulation.
Q11: Which of the following best describes the function of ribosomes in protein synthesis?
A. They store genetic information
B. They catalyze peptide bond formation between amino acids [CORRECT]
C. They transport proteins to the Golgi apparatus
D. They replicate DNA during cell division
Correct Answer: B
Rationale: Correct because the ribosomal RNA (rRNA) within the large ribosomal subunit
possesses peptidyl transferase activity, catalyzing the formation of peptide bonds during
translation. This matches the catalytic function of ribozymes in protein synthesis.
Q12: In the central dogma of molecular biology, information flows in which direction under
normal cellular conditions?
A. Protein → RNA → DNA
B. DNA → RNA → Protein [CORRECT]
C. RNA → DNA → Protein
D. Lipid → Carbohydrate → Protein
Correct Answer: B
Rationale: Correct because the central dogma describes the unidirectional flow of genetic
information from DNA through transcription to RNA, and through translation to functional
proteins. This matches the fundamental paradigm established by molecular biology research.
