Biochemistry: DNA, RNA & Protein Synthesis Practice Pack 2026
|WGU
1. Which of the following describes the primary difference between the sugar
components of DNA and RNA?
A. DNA contains ribose, while RNA contains deoxyribose.
B. RNA contains deoxyribose, while DNA contains ribose.
C. DNA contains deoxyribose, which lacks an oxygen atom at the 2’ carbon position compared to ribose.
D. DNA contains glucose, while RNA contains ribose.
Answer: C
Rationale: DNA stands for Deoxyribonucleic Acid because its sugar is deoxyribose, which
has one less oxygen atom at the 2’ carbon than the ribose sugar found in RNA.
2. Which enzyme is responsible for unwinding the DNA double helix during the
replication process?
A. DNA Polymerase III
B. DNA Ligase
C. Topoisomerase
D. Helicase
Answer: D
Rationale: Helicase breaks the hydrogen bonds between the nitrogenous bases to separate
the two strands of DNA, creating the replication fork.
,3. In DNA replication, what is the role of Single-Strand Binding Proteins (SSBs)?
A. To synthesize RNA primers.
B. To join Okazaki fragments together.
C. To prevent the separated DNA strands from re-annealing.
D. To proofread the newly synthesized DNA strand.
Answer: C
Rationale: SSBs bind to the single-stranded DNA exposed by helicase to stabilize it and
prevent it from forming a double helix again before replication is complete.
4. According to Chargaff’s rules, if a DNA sample contains 20% Adenine, what is
the percentage of Guanine?
A. 30%
B. 80%
C. 20%
D. 60%
Answer: A
Rationale: If Adenine is 20%, then Thymine is also 20% (Total 40%). The remaining 60%
must be split equally between Guanine and Cytosine, so Guanine is 30%.
5. Which type of bond connects the phosphate group of one nucleotide to the
sugar of the next nucleotide in a DNA strand?
A. Hydrogen bond
B. Peptide bond
C. Phosphodiester bond
D. Ionic bond
Answer: C
Rationale: Phosphodiester bonds form the sugar-phosphate backbone of DNA and RNA by
connecting the 3’ carbon of one sugar to the 5’ phosphate of another.
, 6. 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. Randomly in either direction
Answer: B
Rationale: DNA Polymerase can only add new nucleotides to the free 3’ hydroxyl group of
an existing strand, resulting in 5’ to 3’ synthesis.
7. What is the function of DNA Ligase on the lagging strand?
A. Adding RNA primers.
B. Relieving torsional strain ahead of the fork.
C. Joining Okazaki fragments by forming phosphodiester bonds.
D. Removing incorrect base pairs.
Answer: C
Rationale: DNA Ligase ‘glues’ the short Okazaki fragments on the lagging strand together
to create a continuous DNA molecule.
8. Which of the following is NOT a component of a nucleotide?
A. Nitrogenous base
B. Phosphate group
C. Five-carbon sugar
D. Amino acid side chain
Answer: D
Rationale: Nucleotides consist of a sugar, a phosphate, and a nitrogenous base. Amino acid
side chains are components of proteins.
|WGU
1. Which of the following describes the primary difference between the sugar
components of DNA and RNA?
A. DNA contains ribose, while RNA contains deoxyribose.
B. RNA contains deoxyribose, while DNA contains ribose.
C. DNA contains deoxyribose, which lacks an oxygen atom at the 2’ carbon position compared to ribose.
D. DNA contains glucose, while RNA contains ribose.
Answer: C
Rationale: DNA stands for Deoxyribonucleic Acid because its sugar is deoxyribose, which
has one less oxygen atom at the 2’ carbon than the ribose sugar found in RNA.
2. Which enzyme is responsible for unwinding the DNA double helix during the
replication process?
A. DNA Polymerase III
B. DNA Ligase
C. Topoisomerase
D. Helicase
Answer: D
Rationale: Helicase breaks the hydrogen bonds between the nitrogenous bases to separate
the two strands of DNA, creating the replication fork.
,3. In DNA replication, what is the role of Single-Strand Binding Proteins (SSBs)?
A. To synthesize RNA primers.
B. To join Okazaki fragments together.
C. To prevent the separated DNA strands from re-annealing.
D. To proofread the newly synthesized DNA strand.
Answer: C
Rationale: SSBs bind to the single-stranded DNA exposed by helicase to stabilize it and
prevent it from forming a double helix again before replication is complete.
4. According to Chargaff’s rules, if a DNA sample contains 20% Adenine, what is
the percentage of Guanine?
A. 30%
B. 80%
C. 20%
D. 60%
Answer: A
Rationale: If Adenine is 20%, then Thymine is also 20% (Total 40%). The remaining 60%
must be split equally between Guanine and Cytosine, so Guanine is 30%.
5. Which type of bond connects the phosphate group of one nucleotide to the
sugar of the next nucleotide in a DNA strand?
A. Hydrogen bond
B. Peptide bond
C. Phosphodiester bond
D. Ionic bond
Answer: C
Rationale: Phosphodiester bonds form the sugar-phosphate backbone of DNA and RNA by
connecting the 3’ carbon of one sugar to the 5’ phosphate of another.
, 6. 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. Randomly in either direction
Answer: B
Rationale: DNA Polymerase can only add new nucleotides to the free 3’ hydroxyl group of
an existing strand, resulting in 5’ to 3’ synthesis.
7. What is the function of DNA Ligase on the lagging strand?
A. Adding RNA primers.
B. Relieving torsional strain ahead of the fork.
C. Joining Okazaki fragments by forming phosphodiester bonds.
D. Removing incorrect base pairs.
Answer: C
Rationale: DNA Ligase ‘glues’ the short Okazaki fragments on the lagging strand together
to create a continuous DNA molecule.
8. Which of the following is NOT a component of a nucleotide?
A. Nitrogenous base
B. Phosphate group
C. Five-carbon sugar
D. Amino acid side chain
Answer: D
Rationale: Nucleotides consist of a sugar, a phosphate, and a nitrogenous base. Amino acid
side chains are components of proteins.
