C785 Biochemistry Module 5 Quiz 2026 |WGU
1. Which enzyme is responsible for unwinding the DNA double helix during
replication?
A. DNA Polymerase
B. DNA Ligase
C. Helicase
D. Topoisomerase
Answer: C
Rationale: Helicase breaks the hydrogen bonds between the nitrogenous bases to separate
the DNA strands.
2. In which direction is a new DNA strand always synthesized?
A. 3’ to 5’
B. 5’ to 3’
C. N-terminus to C-terminus
D. 5’ to 5’
Answer: B
Rationale: DNA polymerase can only add nucleotides to the 3’ hydroxyl group of the
growing strand, resulting in 5’ to 3’ synthesis.
,3. Which molecule carries the genetic information from the nucleus to the
ribosome?
A. tRNA
B. rRNA
C. mRNA
D. snRNA
Answer: C
Rationale: Messenger RNA (mRNA) is the transcript that carries the genetic code from the
DNA in the nucleus to the cytoplasm for translation.
4. What is the role of DNA Ligase in replication?
A. Unwinding the helix
B. Adding RNA primers
C. Joining Okazaki fragments
D. Stabilizing single strands
Answer: C
Rationale: DNA Ligase seals the nicks between DNA fragments, particularly on the lagging
strand, by forming phosphodiester bonds.
5. Which of the following is a purine?
A. Adenine
B. Thymine
C. Uracil
D. Cytosine
Answer: A
Rationale: Adenine and Guanine are double-ringed purines; Cytosine, Thymine, and Uracil
are single-ringed pyrimidines.
, 6. During transcription, what is the DNA sequence that RNA polymerase binds
to?
A. The Promoter
B. The Origin of Replication
C. The Codon
D. The Enhancer
Answer: A
Rationale: The promoter is a specific DNA sequence that signals the start of a gene and
provides a binding site for RNA polymerase.
7. Which type of mutation results in a premature stop codon?
A. Silent mutation
B. Nonsense mutation
C. Missense mutation
D. Frameshift mutation
Answer: B
Rationale: A nonsense mutation changes a codon for an amino acid into a stop codon,
leading to a truncated protein.
8. What is the purpose of the poly-A tail added to mRNA?
A. To facilitate splicing
B. To code for specific amino acids
C. To serve as a binding site for tRNA
D. To protect the mRNA from degradation
Answer: D
Rationale: The poly-A tail added to the 3’ end of mRNA increases stability and aids in
nuclear export.
1. Which enzyme is responsible for unwinding the DNA double helix during
replication?
A. DNA Polymerase
B. DNA Ligase
C. Helicase
D. Topoisomerase
Answer: C
Rationale: Helicase breaks the hydrogen bonds between the nitrogenous bases to separate
the DNA strands.
2. In which direction is a new DNA strand always synthesized?
A. 3’ to 5’
B. 5’ to 3’
C. N-terminus to C-terminus
D. 5’ to 5’
Answer: B
Rationale: DNA polymerase can only add nucleotides to the 3’ hydroxyl group of the
growing strand, resulting in 5’ to 3’ synthesis.
,3. Which molecule carries the genetic information from the nucleus to the
ribosome?
A. tRNA
B. rRNA
C. mRNA
D. snRNA
Answer: C
Rationale: Messenger RNA (mRNA) is the transcript that carries the genetic code from the
DNA in the nucleus to the cytoplasm for translation.
4. What is the role of DNA Ligase in replication?
A. Unwinding the helix
B. Adding RNA primers
C. Joining Okazaki fragments
D. Stabilizing single strands
Answer: C
Rationale: DNA Ligase seals the nicks between DNA fragments, particularly on the lagging
strand, by forming phosphodiester bonds.
5. Which of the following is a purine?
A. Adenine
B. Thymine
C. Uracil
D. Cytosine
Answer: A
Rationale: Adenine and Guanine are double-ringed purines; Cytosine, Thymine, and Uracil
are single-ringed pyrimidines.
, 6. During transcription, what is the DNA sequence that RNA polymerase binds
to?
A. The Promoter
B. The Origin of Replication
C. The Codon
D. The Enhancer
Answer: A
Rationale: The promoter is a specific DNA sequence that signals the start of a gene and
provides a binding site for RNA polymerase.
7. Which type of mutation results in a premature stop codon?
A. Silent mutation
B. Nonsense mutation
C. Missense mutation
D. Frameshift mutation
Answer: B
Rationale: A nonsense mutation changes a codon for an amino acid into a stop codon,
leading to a truncated protein.
8. What is the purpose of the poly-A tail added to mRNA?
A. To facilitate splicing
B. To code for specific amino acids
C. To serve as a binding site for tRNA
D. To protect the mRNA from degradation
Answer: D
Rationale: The poly-A tail added to the 3’ end of mRNA increases stability and aids in
nuclear export.
