Biochemistry Module 4: DNA, RNA, and Protein Synthesis 2026 |WGU
1. Which of the following components is NOT found in a DNA nucleotide?
A. Phosphate group
B. Deoxyribose sugar
C. Nitrogenous base
D. Uracil
Answer: D
Rationale: DNA contains adenine, thymine, cytosine, and guanine. Uracil is found only in
RNA.
2. In which direction is a new DNA strand always synthesized?
A. 5’ to 3’
B. 3’ to 5’
C. N-terminus to C-terminus
D. Left to right
Answer: A
Rationale: DNA polymerase can only add nucleotides to the 3’ end of a growing strand,
meaning synthesis occurs 5’ to 3’.
3. What enzyme is responsible for unwinding the DNA double helix during
replication?
A. DNA Ligase
B. DNA Polymerase III
C. Primase
D. Helicase
Answer: D
,Rationale: Helicase breaks the hydrogen bonds between bases to unzip the double helix.
4. The lagging strand is synthesized in short segments called:
A. Watson fragments
B. Okazaki fragments
C. Crick segments
D. Primer segments
Answer: B
Rationale: The lagging strand is synthesized discontinuously in short pieces known as
Okazaki fragments.
5. Which enzyme relieves torsional strain (supercoiling) ahead of the replication
fork?
A. DNA Polymerase I
B. Topoisomerase
C. Single-strand binding proteins
D. Primase
Answer: B
Rationale: Topoisomerase (or DNA Gyrase) cuts and reseals the DNA to prevent tangling
during unwinding.
6. What is the role of Primase in DNA replication?
A. To seal nicks in the sugar-phosphate backbone
B. To remove introns from the sequence
C. To proofread the DNA sequence
D. To synthesize a short RNA primer to provide a 3’ OH group
Answer: D
Rationale: DNA polymerase requires a free 3’ hydroxyl group to start; Primase provides
this via an RNA primer.
, 7. DNA replication is described as ‘semi-conservative’ because:
A. The daughter molecule consists of one old strand and one new strand
B. Only half of the DNA is copied
C. The genetic code is partially preserved
D. It only happens in the nucleus
Answer: A
Rationale: Each new DNA double helix consists of one original template strand and one
newly synthesized strand.
8. Which enzyme joins Okazaki fragments together?
A. DNA Polymerase III
B. RNA Polymerase
C. DNA Ligase
D. Helicase
Answer: C
Rationale: Ligase acts as a glue, sealing the phosphodiester bonds between fragments.
9. Where does transcription take place in a eukaryotic cell?
A. Cytoplasm
B. Mitochondria
C. Ribosome
D. Nucleus
Answer: D
Rationale: DNA is housed in the nucleus, so transcription (DNA to RNA) must occur there.
1. Which of the following components is NOT found in a DNA nucleotide?
A. Phosphate group
B. Deoxyribose sugar
C. Nitrogenous base
D. Uracil
Answer: D
Rationale: DNA contains adenine, thymine, cytosine, and guanine. Uracil is found only in
RNA.
2. In which direction is a new DNA strand always synthesized?
A. 5’ to 3’
B. 3’ to 5’
C. N-terminus to C-terminus
D. Left to right
Answer: A
Rationale: DNA polymerase can only add nucleotides to the 3’ end of a growing strand,
meaning synthesis occurs 5’ to 3’.
3. What enzyme is responsible for unwinding the DNA double helix during
replication?
A. DNA Ligase
B. DNA Polymerase III
C. Primase
D. Helicase
Answer: D
,Rationale: Helicase breaks the hydrogen bonds between bases to unzip the double helix.
4. The lagging strand is synthesized in short segments called:
A. Watson fragments
B. Okazaki fragments
C. Crick segments
D. Primer segments
Answer: B
Rationale: The lagging strand is synthesized discontinuously in short pieces known as
Okazaki fragments.
5. Which enzyme relieves torsional strain (supercoiling) ahead of the replication
fork?
A. DNA Polymerase I
B. Topoisomerase
C. Single-strand binding proteins
D. Primase
Answer: B
Rationale: Topoisomerase (or DNA Gyrase) cuts and reseals the DNA to prevent tangling
during unwinding.
6. What is the role of Primase in DNA replication?
A. To seal nicks in the sugar-phosphate backbone
B. To remove introns from the sequence
C. To proofread the DNA sequence
D. To synthesize a short RNA primer to provide a 3’ OH group
Answer: D
Rationale: DNA polymerase requires a free 3’ hydroxyl group to start; Primase provides
this via an RNA primer.
, 7. DNA replication is described as ‘semi-conservative’ because:
A. The daughter molecule consists of one old strand and one new strand
B. Only half of the DNA is copied
C. The genetic code is partially preserved
D. It only happens in the nucleus
Answer: A
Rationale: Each new DNA double helix consists of one original template strand and one
newly synthesized strand.
8. Which enzyme joins Okazaki fragments together?
A. DNA Polymerase III
B. RNA Polymerase
C. DNA Ligase
D. Helicase
Answer: C
Rationale: Ligase acts as a glue, sealing the phosphodiester bonds between fragments.
9. Where does transcription take place in a eukaryotic cell?
A. Cytoplasm
B. Mitochondria
C. Ribosome
D. Nucleus
Answer: D
Rationale: DNA is housed in the nucleus, so transcription (DNA to RNA) must occur there.
