C785 Biochemistry Module 5 Comprehensive Review 2026 |WGU
1. Which enzyme is responsible for unwinding the DNA double helix during DNA
replication?
A. DNA Polymerase
B. Primase
C. Ligase
D. Helicase
Answer: D
Rationale: Helicase breaks the hydrogen bonds between the nitrogenous bases to separate
the two strands of the DNA double helix.
2. In which direction is a new DNA strand always synthesized?
A. 3’ to 5’
B. 5’ to 3’
C. C-terminus to N-terminus
D. N-terminus to C-terminus
Answer: B
Rationale: DNA polymerases can only add nucleotides to the 3’ hydroxyl group of a
growing chain, meaning synthesis occurs in the 5’ to 3’ direction.
,3. Which molecule contains the anticodon and carries a specific amino acid to
the ribosome?
A. mRNA
B. tRNA
C. rRNA
D. snRNA
Answer: B
Rationale: tRNA (transfer RNA) serves as the adapter molecule that matches a specific
codon on mRNA with its corresponding amino acid.
4. What is the primary function of DNA Polymerase III in prokaryotes?
A. Removing RNA primers
B. Unwinding DNA
C. Synthesizing the leading and lagging strands
D. Sealing nicks in the sugar-phosphate backbone
Answer: C
Rationale: DNA Polymerase III is the primary enzyme involved in the synthesis of new
DNA strands by adding nucleotides.
5. Which process involves the removal of introns and the joining of exons?
A. Transcription
B. Translation
C. Replication
D. Splicing
Answer: D
Rationale: Splicing is a post-transcriptional modification where non-coding introns are
removed and coding exons are joined together.
, 6. A mutation that changes a codon for an amino acid into a stop codon is called
a:
A. Silent mutation
B. Missense mutation
C. Frameshift mutation
D. Nonsense mutation
Answer: D
Rationale: Nonsense mutations create a premature stop codon, leading to a truncated and
usually non-functional protein.
7. Which of the following is characteristic of the ‘wobble’ position in
translation?
A. It occurs at the first base of the codon
B. It always results in a missense mutation
C. It makes the genetic code ambiguous
D. It allows one tRNA to recognize multiple codons
Answer: D
Rationale: The wobble position is the 3rd base of the codon, allowing flexibility in base
pairing and reducing the number of tRNAs needed.
8. Which enzyme seals the gaps between Okazaki fragments on the lagging
strand?
A. DNA Ligase
B. Helicase
C. Topoisomerase
D. RNA Polymerase
Answer: A
Rationale: DNA Ligase catalyzes the formation of a phosphodiester bond to seal the ‘nick’
between DNA fragments.
1. Which enzyme is responsible for unwinding the DNA double helix during DNA
replication?
A. DNA Polymerase
B. Primase
C. Ligase
D. Helicase
Answer: D
Rationale: Helicase breaks the hydrogen bonds between the nitrogenous bases to separate
the two strands of the DNA double helix.
2. In which direction is a new DNA strand always synthesized?
A. 3’ to 5’
B. 5’ to 3’
C. C-terminus to N-terminus
D. N-terminus to C-terminus
Answer: B
Rationale: DNA polymerases can only add nucleotides to the 3’ hydroxyl group of a
growing chain, meaning synthesis occurs in the 5’ to 3’ direction.
,3. Which molecule contains the anticodon and carries a specific amino acid to
the ribosome?
A. mRNA
B. tRNA
C. rRNA
D. snRNA
Answer: B
Rationale: tRNA (transfer RNA) serves as the adapter molecule that matches a specific
codon on mRNA with its corresponding amino acid.
4. What is the primary function of DNA Polymerase III in prokaryotes?
A. Removing RNA primers
B. Unwinding DNA
C. Synthesizing the leading and lagging strands
D. Sealing nicks in the sugar-phosphate backbone
Answer: C
Rationale: DNA Polymerase III is the primary enzyme involved in the synthesis of new
DNA strands by adding nucleotides.
5. Which process involves the removal of introns and the joining of exons?
A. Transcription
B. Translation
C. Replication
D. Splicing
Answer: D
Rationale: Splicing is a post-transcriptional modification where non-coding introns are
removed and coding exons are joined together.
, 6. A mutation that changes a codon for an amino acid into a stop codon is called
a:
A. Silent mutation
B. Missense mutation
C. Frameshift mutation
D. Nonsense mutation
Answer: D
Rationale: Nonsense mutations create a premature stop codon, leading to a truncated and
usually non-functional protein.
7. Which of the following is characteristic of the ‘wobble’ position in
translation?
A. It occurs at the first base of the codon
B. It always results in a missense mutation
C. It makes the genetic code ambiguous
D. It allows one tRNA to recognize multiple codons
Answer: D
Rationale: The wobble position is the 3rd base of the codon, allowing flexibility in base
pairing and reducing the number of tRNAs needed.
8. Which enzyme seals the gaps between Okazaki fragments on the lagging
strand?
A. DNA Ligase
B. Helicase
C. Topoisomerase
D. RNA Polymerase
Answer: A
Rationale: DNA Ligase catalyzes the formation of a phosphodiester bond to seal the ‘nick’
between DNA fragments.
