Biochemistry Module 2 Comprehensive Review 2026 |WGU
1. Which component of a nucleotide is responsible for the genetic code’s
information storage?
A. The phosphate group
B. The pentose sugar
C. The hydroxyl group
D. The nitrogenous base
Answer: D
Rationale: The nitrogenous bases (A, T, C, G in DNA; A, U, C, G in RNA) are the variable
components that sequence the genetic information.
2. Which type of bond connects the sugar-phosphate backbone in DNA?
A. Hydrogen bond
B. Peptide bond
C. Ionic bond
D. Phosphodiester bond
Answer: D
Rationale: Phosphodiester bonds are covalent bonds that link the 3’ carbon of one sugar to
the 5’ carbon of the next.
,3. In a DNA double helix, how many hydrogen bonds form between Guanine
and Cytosine?
A. One
B. Three
C. Two
D. Four
Answer: B
Rationale: G-C pairs are held together by three hydrogen bonds, making them stronger
than A-T pairs which have two.
4. What is the primary difference between the sugars found in DNA and RNA?
A. DNA contains deoxyribose, which lacks an oxygen atom at the 2’ carbon
B. RNA contains glucose; DNA contains ribose
C. RNA contains a hexose sugar; DNA contains a pentose sugar
D. There is no difference in the sugars
Answer: A
Rationale: Deoxyribose in DNA has a hydrogen instead of a hydroxyl group at the 2’
position, which increases DNA’s stability compared to RNA.
5. During DNA replication, which enzyme is responsible for unwinding the
double helix?
A. DNA Polymerase
B. DNA Ligase
C. Primase
D. Helicase
Answer: D
Rationale: Helicase breaks the hydrogen bonds between bases to unzip the DNA strands
for replication.
, 6. Which enzyme synthesizes short RNA sequences to initiate DNA replication?
A. Primase
B. DNA Polymerase III
C. Topoisomerase
D. Exonuclease
Answer: A
Rationale: DNA polymerase cannot start a strand from scratch; Primase provides the RNA
primer needed to begin synthesis.
7. In which direction is a new DNA strand always synthesized?
A. 5’ to 3’
B. 3’ to 5’
C. C-terminus to N-terminus
D. Randomly
Answer: A
Rationale: DNA Polymerase adds new nucleotides only to the 3’ end of the growing strand.
8. What are Okazaki fragments?
A. The fragments of the leading strand
B. Short segments of DNA synthesized on the lagging strand
C. RNA primers that have been removed
D. Mutated DNA sequences
Answer: B
Rationale: Because the lagging strand is antiparallel, it must be synthesized in short,
discontinuous segments called Okazaki fragments.
1. Which component of a nucleotide is responsible for the genetic code’s
information storage?
A. The phosphate group
B. The pentose sugar
C. The hydroxyl group
D. The nitrogenous base
Answer: D
Rationale: The nitrogenous bases (A, T, C, G in DNA; A, U, C, G in RNA) are the variable
components that sequence the genetic information.
2. Which type of bond connects the sugar-phosphate backbone in DNA?
A. Hydrogen bond
B. Peptide bond
C. Ionic bond
D. Phosphodiester bond
Answer: D
Rationale: Phosphodiester bonds are covalent bonds that link the 3’ carbon of one sugar to
the 5’ carbon of the next.
,3. In a DNA double helix, how many hydrogen bonds form between Guanine
and Cytosine?
A. One
B. Three
C. Two
D. Four
Answer: B
Rationale: G-C pairs are held together by three hydrogen bonds, making them stronger
than A-T pairs which have two.
4. What is the primary difference between the sugars found in DNA and RNA?
A. DNA contains deoxyribose, which lacks an oxygen atom at the 2’ carbon
B. RNA contains glucose; DNA contains ribose
C. RNA contains a hexose sugar; DNA contains a pentose sugar
D. There is no difference in the sugars
Answer: A
Rationale: Deoxyribose in DNA has a hydrogen instead of a hydroxyl group at the 2’
position, which increases DNA’s stability compared to RNA.
5. During DNA replication, which enzyme is responsible for unwinding the
double helix?
A. DNA Polymerase
B. DNA Ligase
C. Primase
D. Helicase
Answer: D
Rationale: Helicase breaks the hydrogen bonds between bases to unzip the DNA strands
for replication.
, 6. Which enzyme synthesizes short RNA sequences to initiate DNA replication?
A. Primase
B. DNA Polymerase III
C. Topoisomerase
D. Exonuclease
Answer: A
Rationale: DNA polymerase cannot start a strand from scratch; Primase provides the RNA
primer needed to begin synthesis.
7. In which direction is a new DNA strand always synthesized?
A. 5’ to 3’
B. 3’ to 5’
C. C-terminus to N-terminus
D. Randomly
Answer: A
Rationale: DNA Polymerase adds new nucleotides only to the 3’ end of the growing strand.
8. What are Okazaki fragments?
A. The fragments of the leading strand
B. Short segments of DNA synthesized on the lagging strand
C. RNA primers that have been removed
D. Mutated DNA sequences
Answer: B
Rationale: Because the lagging strand is antiparallel, it must be synthesized in short,
discontinuous segments called Okazaki fragments.
