C785 Biochemistry Week 5 Practice Questions 2026 |WGU
1. Which enzyme is responsible for synthesizing the RNA primer during DNA
replication?
A. DNA Polymerase I
B. Primase
C. DNA Ligase
D. Helicase
Answer: B
Rationale: Primase is a type of RNA polymerase that creates a short RNA primer to
provide a 3’-OH group for DNA polymerase to begin synthesis.
2. In DNA replication, what is the role of Single-Strand Binding (SSB) proteins?
A. To unzip the double helix
B. To prevent the separated strands from re-annealing
C. To proofread the new DNA strand
D. To connect Okazaki fragments
Answer: B
Rationale: SSB proteins bind to the single-stranded DNA to stabilize it and prevent it from
reforming a double helix during replication.
3. Which of the following describes the direction of DNA synthesis?
A. 3’ to 5’ on both strands
B. 5’ to 3’ on both strands
C. 5’ to 3’ on the leading strand and 3’ to 5’ on the lagging strand
D. Randomly depending on the enzyme
Answer: B
,Rationale: DNA polymerase can only add nucleotides to the 3’ end of a growing strand,
meaning synthesis always occurs in the 5’ to 3’ direction.
4. What type of bond connects the phosphate group of one nucleotide to the
sugar of the next?
A. Hydrogen bond
B. Phosphodiester bond
C. Peptide bond
D. Ionic bond
Answer: B
Rationale: A phosphodiester bond forms the backbone of the DNA and RNA strands by
linking the 5’ phosphate of one nucleotide to the 3’ hydroxyl of another.
5. Which repair mechanism is specifically used to fix thymine dimers caused by
UV light?
A. Nucleotide Excision Repair (NER)
B. Mismatch Repair (MMR)
C. Base Excision Repair (BER)
D. Homologous Recombination
Answer: A
Rationale: NER is responsible for removing bulky lesions, such as pyrimidine (thymine)
dimers, by cutting out a segment of the DNA strand.
6. Which nitrogenous base is found in RNA but not in DNA?
A. Adenine
B. Uracil
C. Guanine
D. Thymine
Answer: B
, Rationale: RNA contains Uracil (U) instead of Thymine (T), which is found in DNA.
7. Which enzyme relieves the torsional strain (supercoiling) ahead of the
replication fork?
A. Helicase
B. Topoisomerase
C. DNA Polymerase III
D. Telomerase
Answer: B
Rationale: Topoisomerase (or DNA Gyrase in prokaryotes) cuts and reseals the DNA to
relieve tension caused by unwinding.
8. What is the function of the promoter region in a gene?
A. To signal the end of transcription
B. To provide a binding site for RNA polymerase
C. To code for the protein sequence
D. To catalyze the formation of peptide bonds
Answer: B
Rationale: The promoter is a specific DNA sequence where RNA polymerase binds to
initiate the transcription of a gene.
9. Which of the following is a characteristic of the genetic code?
A. It is overlapping
B. It is ambiguous
C. It is redundant (degenerate)
D. It varies significantly between species
Answer: C
Rationale: The genetic code is redundant, meaning multiple codons can code for the same
amino acid (e.g., Leu has six codons).
1. Which enzyme is responsible for synthesizing the RNA primer during DNA
replication?
A. DNA Polymerase I
B. Primase
C. DNA Ligase
D. Helicase
Answer: B
Rationale: Primase is a type of RNA polymerase that creates a short RNA primer to
provide a 3’-OH group for DNA polymerase to begin synthesis.
2. In DNA replication, what is the role of Single-Strand Binding (SSB) proteins?
A. To unzip the double helix
B. To prevent the separated strands from re-annealing
C. To proofread the new DNA strand
D. To connect Okazaki fragments
Answer: B
Rationale: SSB proteins bind to the single-stranded DNA to stabilize it and prevent it from
reforming a double helix during replication.
3. Which of the following describes the direction of DNA synthesis?
A. 3’ to 5’ on both strands
B. 5’ to 3’ on both strands
C. 5’ to 3’ on the leading strand and 3’ to 5’ on the lagging strand
D. Randomly depending on the enzyme
Answer: B
,Rationale: DNA polymerase can only add nucleotides to the 3’ end of a growing strand,
meaning synthesis always occurs in the 5’ to 3’ direction.
4. What type of bond connects the phosphate group of one nucleotide to the
sugar of the next?
A. Hydrogen bond
B. Phosphodiester bond
C. Peptide bond
D. Ionic bond
Answer: B
Rationale: A phosphodiester bond forms the backbone of the DNA and RNA strands by
linking the 5’ phosphate of one nucleotide to the 3’ hydroxyl of another.
5. Which repair mechanism is specifically used to fix thymine dimers caused by
UV light?
A. Nucleotide Excision Repair (NER)
B. Mismatch Repair (MMR)
C. Base Excision Repair (BER)
D. Homologous Recombination
Answer: A
Rationale: NER is responsible for removing bulky lesions, such as pyrimidine (thymine)
dimers, by cutting out a segment of the DNA strand.
6. Which nitrogenous base is found in RNA but not in DNA?
A. Adenine
B. Uracil
C. Guanine
D. Thymine
Answer: B
, Rationale: RNA contains Uracil (U) instead of Thymine (T), which is found in DNA.
7. Which enzyme relieves the torsional strain (supercoiling) ahead of the
replication fork?
A. Helicase
B. Topoisomerase
C. DNA Polymerase III
D. Telomerase
Answer: B
Rationale: Topoisomerase (or DNA Gyrase in prokaryotes) cuts and reseals the DNA to
relieve tension caused by unwinding.
8. What is the function of the promoter region in a gene?
A. To signal the end of transcription
B. To provide a binding site for RNA polymerase
C. To code for the protein sequence
D. To catalyze the formation of peptide bonds
Answer: B
Rationale: The promoter is a specific DNA sequence where RNA polymerase binds to
initiate the transcription of a gene.
9. Which of the following is a characteristic of the genetic code?
A. It is overlapping
B. It is ambiguous
C. It is redundant (degenerate)
D. It varies significantly between species
Answer: C
Rationale: The genetic code is redundant, meaning multiple codons can code for the same
amino acid (e.g., Leu has six codons).
