C785 Biochemistry Module 6: DNA, RNA, and Protein Synthesis 2026
|WGU
1. Which of the following components are found in a single DNA nucleotide?
A. Deoxyribose sugar, nitrogenous base, and phosphate group
B. Ribose sugar, nitrogenous base, and phosphate group
C. Deoxyribose sugar, amino acid, and phosphate group
D. Ribose sugar, nitrogenous base, and sulfate group
Answer: A
Rationale: A DNA nucleotide consists of a deoxyribose sugar, one of four nitrogenous
bases, and a phosphate group.
2. In DNA replication, which enzyme is responsible for unwinding the double
helix?
A. Helicase
B. Topoisomerase
C. DNA Polymerase
D. Ligase
Answer: A
Rationale: Helicase breaks the hydrogen bonds between base pairs to unwind and
separate the DNA strands.
,3. DNA replication is described as ‘semi-conservative’ because:
A. Both strands of the new DNA molecule are entirely new.
B. The parent DNA remains intact and a completely new double helix is formed.
C. Only half of the genes are replicated.
D. The daughter DNA molecule consists of one original parent strand and one new strand.
Answer: D
Rationale: Semi-conservative replication means each new DNA molecule conserves one of
the original strands from the parent molecule.
4. Which nitrogenous base is found in RNA but not in DNA?
A. Thymine
B. Adenine
C. Guanine
D. Uracil
Answer: D
Rationale: In RNA, Uracil replaces Thymine, which is found in DNA.
5. What is the direction of DNA synthesis by DNA polymerase?
A. 3’ to 5’
B. 5’ to 3’
C. Left to right only
D. Both 3’ to 5’ and 5’ to 3’
Answer: B
Rationale: DNA polymerase can only add nucleotides to the 3’ end of a growing strand,
meaning synthesis occurs in the 5’ to 3’ direction.
, 6. The short fragments of DNA produced on the lagging strand are called:
A. Primers
B. Okazaki fragments
C. Promoters
D. Introns
Answer: B
Rationale: Because the lagging strand is synthesized discontinuously, it forms short
segments known as Okazaki fragments.
7. Which enzyme joins Okazaki fragments together?
A. RNA Polymerase
B. DNA Ligase
C. Helicase
D. Primase
Answer: B
Rationale: DNA Ligase ‘glues’ or seals the nicks between DNA fragments by forming
phosphodiester bonds.
8. What is the function of Topoisomerase during replication?
A. Relieving torsional strain (overwinding) ahead of the replication fork
B. Synthesizing RNA primers
C. Adding telomeres to the ends of chromosomes
D. Proofreading the DNA sequence
Answer: A
Rationale: Topoisomerase cuts and rejoins DNA strands to prevent supercoiling and
tension during unwinding.
|WGU
1. Which of the following components are found in a single DNA nucleotide?
A. Deoxyribose sugar, nitrogenous base, and phosphate group
B. Ribose sugar, nitrogenous base, and phosphate group
C. Deoxyribose sugar, amino acid, and phosphate group
D. Ribose sugar, nitrogenous base, and sulfate group
Answer: A
Rationale: A DNA nucleotide consists of a deoxyribose sugar, one of four nitrogenous
bases, and a phosphate group.
2. In DNA replication, which enzyme is responsible for unwinding the double
helix?
A. Helicase
B. Topoisomerase
C. DNA Polymerase
D. Ligase
Answer: A
Rationale: Helicase breaks the hydrogen bonds between base pairs to unwind and
separate the DNA strands.
,3. DNA replication is described as ‘semi-conservative’ because:
A. Both strands of the new DNA molecule are entirely new.
B. The parent DNA remains intact and a completely new double helix is formed.
C. Only half of the genes are replicated.
D. The daughter DNA molecule consists of one original parent strand and one new strand.
Answer: D
Rationale: Semi-conservative replication means each new DNA molecule conserves one of
the original strands from the parent molecule.
4. Which nitrogenous base is found in RNA but not in DNA?
A. Thymine
B. Adenine
C. Guanine
D. Uracil
Answer: D
Rationale: In RNA, Uracil replaces Thymine, which is found in DNA.
5. What is the direction of DNA synthesis by DNA polymerase?
A. 3’ to 5’
B. 5’ to 3’
C. Left to right only
D. Both 3’ to 5’ and 5’ to 3’
Answer: B
Rationale: DNA polymerase can only add nucleotides to the 3’ end of a growing strand,
meaning synthesis occurs in the 5’ to 3’ direction.
, 6. The short fragments of DNA produced on the lagging strand are called:
A. Primers
B. Okazaki fragments
C. Promoters
D. Introns
Answer: B
Rationale: Because the lagging strand is synthesized discontinuously, it forms short
segments known as Okazaki fragments.
7. Which enzyme joins Okazaki fragments together?
A. RNA Polymerase
B. DNA Ligase
C. Helicase
D. Primase
Answer: B
Rationale: DNA Ligase ‘glues’ or seals the nicks between DNA fragments by forming
phosphodiester bonds.
8. What is the function of Topoisomerase during replication?
A. Relieving torsional strain (overwinding) ahead of the replication fork
B. Synthesizing RNA primers
C. Adding telomeres to the ends of chromosomes
D. Proofreading the DNA sequence
Answer: A
Rationale: Topoisomerase cuts and rejoins DNA strands to prevent supercoiling and
tension during unwinding.
