C785 Biochemistry Week 8 Study Guide 2026 |WGU
1. Which enzyme is responsible for unwinding the DNA double helix during
replication?
A. DNA Polymerase
B. Topoisomerase
C. DNA Ligase
D. Helicase
Answer: D
Rationale: Helicase breaks the hydrogen bonds between nitrogenous bases to unzip the
DNA strand for replication.
2. In which direction is the new DNA strand always synthesized?
A. 5’ to 3’
B. 5’ to 5’
C. 3’ to 5’
D. 3’ to 3’
Answer: A
Rationale: DNA polymerase adds nucleotides only to the 3’ end of the growing strand,
making synthesis 5’ to 3’.
3. Which enzyme joins Okazaki fragments on the lagging strand?
A. DNA Ligase
B. DNA Polymerase I
C. DNA Polymerase III
D. Primase
Answer: A
,Rationale: DNA Ligase seals the gaps between DNA fragments by creating phosphodiester
bonds.
4. What is the primary role of the promoter region in a gene?
A. To signal the end of transcription
B. To protect the mRNA from degradation
C. To provide the code for the protein
D. To serve as a binding site for RNA polymerase
Answer: D
Rationale: The promoter is a specific sequence where RNA polymerase binds to initiate
transcription.
5. Which type of RNA carries the genetic code from the nucleus to the
ribosome?
A. tRNA
B. mRNA
C. rRNA
D. snRNA
Answer: B
Rationale: Messenger RNA (mRNA) acts as the intermediary between DNA and protein
synthesis.
6. What is the process of removing non-coding sequences from pre-mRNA?
A. Capping
B. Splicing
C. Polyadenylation
D. Methylation
Answer: B
Rationale: Splicing removes introns and joins exons together to form a mature mRNA
transcript.
, 7. Which nitrogenous base is found in RNA but not in DNA?
A. Thymine
B. Cytosine
C. Adenine
D. Uracil
Answer: D
Rationale: RNA uses Uracil (U) instead of Thymine (T) which is found in DNA.
8. A sequence of three nucleotides on tRNA that pairs with mRNA is called:
A. Codon
B. Intron
C. Exon
D. Anticodon
Answer: D
Rationale: The anticodon on tRNA recognizes and base-pairs with the complementary
codon on mRNA.
9. What occurs during the elongation phase of translation?
A. The ribosome binds to the mRNA
B. The stop codon is recognized
C. Amino acids are added to the growing polypeptide chain
D. The mRNA is transcribed from DNA
Answer: C
Rationale: Elongation is the middle stage where the protein chain grows through peptide
bond formation.
1. Which enzyme is responsible for unwinding the DNA double helix during
replication?
A. DNA Polymerase
B. Topoisomerase
C. DNA Ligase
D. Helicase
Answer: D
Rationale: Helicase breaks the hydrogen bonds between nitrogenous bases to unzip the
DNA strand for replication.
2. In which direction is the new DNA strand always synthesized?
A. 5’ to 3’
B. 5’ to 5’
C. 3’ to 5’
D. 3’ to 3’
Answer: A
Rationale: DNA polymerase adds nucleotides only to the 3’ end of the growing strand,
making synthesis 5’ to 3’.
3. Which enzyme joins Okazaki fragments on the lagging strand?
A. DNA Ligase
B. DNA Polymerase I
C. DNA Polymerase III
D. Primase
Answer: A
,Rationale: DNA Ligase seals the gaps between DNA fragments by creating phosphodiester
bonds.
4. What is the primary role of the promoter region in a gene?
A. To signal the end of transcription
B. To protect the mRNA from degradation
C. To provide the code for the protein
D. To serve as a binding site for RNA polymerase
Answer: D
Rationale: The promoter is a specific sequence where RNA polymerase binds to initiate
transcription.
5. Which type of RNA carries the genetic code from the nucleus to the
ribosome?
A. tRNA
B. mRNA
C. rRNA
D. snRNA
Answer: B
Rationale: Messenger RNA (mRNA) acts as the intermediary between DNA and protein
synthesis.
6. What is the process of removing non-coding sequences from pre-mRNA?
A. Capping
B. Splicing
C. Polyadenylation
D. Methylation
Answer: B
Rationale: Splicing removes introns and joins exons together to form a mature mRNA
transcript.
, 7. Which nitrogenous base is found in RNA but not in DNA?
A. Thymine
B. Cytosine
C. Adenine
D. Uracil
Answer: D
Rationale: RNA uses Uracil (U) instead of Thymine (T) which is found in DNA.
8. A sequence of three nucleotides on tRNA that pairs with mRNA is called:
A. Codon
B. Intron
C. Exon
D. Anticodon
Answer: D
Rationale: The anticodon on tRNA recognizes and base-pairs with the complementary
codon on mRNA.
9. What occurs during the elongation phase of translation?
A. The ribosome binds to the mRNA
B. The stop codon is recognized
C. Amino acids are added to the growing polypeptide chain
D. The mRNA is transcribed from DNA
Answer: C
Rationale: Elongation is the middle stage where the protein chain grows through peptide
bond formation.
