Biochemistry Modules 5–6 Comprehensive Quiz 2026 |WGU
1. Which enzyme is primarily responsible for synthesizing a new DNA strand by
adding nucleotides to a pre-existing 3’ end?
A. DNA Ligase
B. DNA Polymerase
C. Helicase
D. RNA Primase
Answer: B
Rationale: DNA Polymerase is the enzyme that adds deoxyribonucleotides to the 3’
hydroxyl group of a growing DNA chain during replication.
2. In the process of transcription, what is the role of the promoter region?
A. It serves as the binding site for RNA polymerase to initiate transcription
B. It is the site where translation begins
C. It marks the end of a gene sequence
D. It encodes for the poly-A tail
Answer: A
Rationale: The promoter is a specific DNA sequence located upstream of a gene that
signals RNA polymerase to bind and start transcribing RNA.
,3. Which molecule contains the anticodon and carries a specific amino acid to
the ribosome?
A. mRNA
B. rRNA
C. tRNA
D. snRNA
Answer: C
Rationale: Transfer RNA (tRNA) has an anticodon that base-pairs with a codon on mRNA,
ensuring the correct amino acid is added to the polypeptide chain.
4. What is the effect of DNA methylation on gene expression?
A. It generally increases gene expression by loosening chromatin
B. It generally decreases gene expression by promoting a highly condensed chromatin state
C. It has no effect on gene expression
D. It triggers immediate DNA degradation
Answer: B
Rationale: Methylation of DNA, typically at CpG islands, leads to chromatin condensation
(heterochromatin) which prevents transcription factors from binding, thus silencing the
gene.
5. Which type of mutation results in a premature stop codon in the mRNA
sequence?
A. Nonsense mutation
B. Missense mutation
C. Silent mutation
D. Frameshift mutation
Answer: A
Rationale: A nonsense mutation is a point mutation that changes a codon for an amino acid
into a stop codon, leading to a truncated and usually non-functional protein.
, 6. What is the primary product of glycolysis that enters the mitochondria under
aerobic conditions?
A. Lactate
B. Acetyl-CoA
C. Oxaloacetate
D. Pyruvate
Answer: D
Rationale: Glycolysis breaks down glucose into two molecules of pyruvate, which are then
transported into the mitochondria for further oxidation.
7. Where does the Citric Acid Cycle (Krebs Cycle) take place within the cell?
A. Cytosol
B. Nucleus
C. Inner mitochondrial membrane
D. Mitochondrial matrix
Answer: D
Rationale: The enzymes for the Citric Acid Cycle are located in the mitochondrial matrix,
where Acetyl-CoA is oxidized to CO2.
8. In the Electron Transport Chain, what is the final electron acceptor?
A. NADH
B. FADH2
C. Oxygen
D. Water
Answer: C
Rationale: Oxygen acts as the final electron acceptor at the end of the ETC, combining with
electrons and protons to form water.
1. Which enzyme is primarily responsible for synthesizing a new DNA strand by
adding nucleotides to a pre-existing 3’ end?
A. DNA Ligase
B. DNA Polymerase
C. Helicase
D. RNA Primase
Answer: B
Rationale: DNA Polymerase is the enzyme that adds deoxyribonucleotides to the 3’
hydroxyl group of a growing DNA chain during replication.
2. In the process of transcription, what is the role of the promoter region?
A. It serves as the binding site for RNA polymerase to initiate transcription
B. It is the site where translation begins
C. It marks the end of a gene sequence
D. It encodes for the poly-A tail
Answer: A
Rationale: The promoter is a specific DNA sequence located upstream of a gene that
signals RNA polymerase to bind and start transcribing RNA.
,3. Which molecule contains the anticodon and carries a specific amino acid to
the ribosome?
A. mRNA
B. rRNA
C. tRNA
D. snRNA
Answer: C
Rationale: Transfer RNA (tRNA) has an anticodon that base-pairs with a codon on mRNA,
ensuring the correct amino acid is added to the polypeptide chain.
4. What is the effect of DNA methylation on gene expression?
A. It generally increases gene expression by loosening chromatin
B. It generally decreases gene expression by promoting a highly condensed chromatin state
C. It has no effect on gene expression
D. It triggers immediate DNA degradation
Answer: B
Rationale: Methylation of DNA, typically at CpG islands, leads to chromatin condensation
(heterochromatin) which prevents transcription factors from binding, thus silencing the
gene.
5. Which type of mutation results in a premature stop codon in the mRNA
sequence?
A. Nonsense mutation
B. Missense mutation
C. Silent mutation
D. Frameshift mutation
Answer: A
Rationale: A nonsense mutation is a point mutation that changes a codon for an amino acid
into a stop codon, leading to a truncated and usually non-functional protein.
, 6. What is the primary product of glycolysis that enters the mitochondria under
aerobic conditions?
A. Lactate
B. Acetyl-CoA
C. Oxaloacetate
D. Pyruvate
Answer: D
Rationale: Glycolysis breaks down glucose into two molecules of pyruvate, which are then
transported into the mitochondria for further oxidation.
7. Where does the Citric Acid Cycle (Krebs Cycle) take place within the cell?
A. Cytosol
B. Nucleus
C. Inner mitochondrial membrane
D. Mitochondrial matrix
Answer: D
Rationale: The enzymes for the Citric Acid Cycle are located in the mitochondrial matrix,
where Acetyl-CoA is oxidized to CO2.
8. In the Electron Transport Chain, what is the final electron acceptor?
A. NADH
B. FADH2
C. Oxygen
D. Water
Answer: C
Rationale: Oxygen acts as the final electron acceptor at the end of the ETC, combining with
electrons and protons to form water.
