Biochemistry C785 Week 3 Study Guide Quiz 2026 |WGU
1. Which component of a nucleotide is responsible for the negative charge of
DNA?
A. Nitrogenous base
B. Phosphate group
C. Pentose sugar
D. Hydroxyl group
Answer: B
Rationale: The phosphate group in the backbone of DNA and RNA carries a negative
charge, making the entire molecule acidic and negatively charged.
2. Which type of bond connects the sugar of one nucleotide to the phosphate of
the next in a DNA strand?
A. Hydrogen bond
B. Peptide bond
C. Phosphodiester bond
D. Ionic bond
Answer: C
Rationale: Phosphodiester bonds are covalent bonds that form the backbone of DNA and
RNA by linking the 3’ carbon of one sugar to the 5’ phosphate of another.
,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: Guanine and Cytosine form three hydrogen bonds, making their pairing
stronger than the Adenine-Thymine pair, which only forms two.
4. Which enzyme is responsible for unwinding the DNA double helix during
replication?
A. DNA Polymerase
B. Helicase
C. Ligase
D. Primase
Answer: B
Rationale: Helicase breaks the hydrogen bonds between nitrogenous bases to separate the
two strands of DNA for replication.
5. What is the primary function of DNA Polymerase III?
A. To unwind the DNA helix
B. To synthesize new DNA strands by adding nucleotides
C. To join Okazaki fragments
D. To create an RNA primer
Answer: B
Rationale: DNA Polymerase III is the main enzyme that adds nucleotides to the 3’ end of a
growing DNA strand during replication.
, 6. What is the role of Primase in DNA replication?
A. To seal nicks in the phosphate backbone
B. To remove mismatched bases
C. To synthesize a short RNA sequence to provide a 3’ OH group
D. To stabilize single-stranded DNA
Answer: C
Rationale: DNA polymerase cannot start a new strand from scratch; Primase provides the
necessary RNA primer to initiate synthesis.
7. Which strand is synthesized continuously in the same direction as the
replication fork movement?
A. Lagging strand
B. Coding strand
C. Template strand
D. Leading strand
Answer: D
Rationale: The leading strand is synthesized continuously in the 5’ to 3’ direction toward
the replication fork.
8. What are the short segments of DNA synthesized on the lagging strand
called?
A. Primers
B. Exons
C. Okazaki fragments
D. Introns
Answer: C
Rationale: Okazaki fragments are small DNA pieces synthesized discontinuously on the
lagging strand away from the replication fork.
1. Which component of a nucleotide is responsible for the negative charge of
DNA?
A. Nitrogenous base
B. Phosphate group
C. Pentose sugar
D. Hydroxyl group
Answer: B
Rationale: The phosphate group in the backbone of DNA and RNA carries a negative
charge, making the entire molecule acidic and negatively charged.
2. Which type of bond connects the sugar of one nucleotide to the phosphate of
the next in a DNA strand?
A. Hydrogen bond
B. Peptide bond
C. Phosphodiester bond
D. Ionic bond
Answer: C
Rationale: Phosphodiester bonds are covalent bonds that form the backbone of DNA and
RNA by linking the 3’ carbon of one sugar to the 5’ phosphate of another.
,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: Guanine and Cytosine form three hydrogen bonds, making their pairing
stronger than the Adenine-Thymine pair, which only forms two.
4. Which enzyme is responsible for unwinding the DNA double helix during
replication?
A. DNA Polymerase
B. Helicase
C. Ligase
D. Primase
Answer: B
Rationale: Helicase breaks the hydrogen bonds between nitrogenous bases to separate the
two strands of DNA for replication.
5. What is the primary function of DNA Polymerase III?
A. To unwind the DNA helix
B. To synthesize new DNA strands by adding nucleotides
C. To join Okazaki fragments
D. To create an RNA primer
Answer: B
Rationale: DNA Polymerase III is the main enzyme that adds nucleotides to the 3’ end of a
growing DNA strand during replication.
, 6. What is the role of Primase in DNA replication?
A. To seal nicks in the phosphate backbone
B. To remove mismatched bases
C. To synthesize a short RNA sequence to provide a 3’ OH group
D. To stabilize single-stranded DNA
Answer: C
Rationale: DNA polymerase cannot start a new strand from scratch; Primase provides the
necessary RNA primer to initiate synthesis.
7. Which strand is synthesized continuously in the same direction as the
replication fork movement?
A. Lagging strand
B. Coding strand
C. Template strand
D. Leading strand
Answer: D
Rationale: The leading strand is synthesized continuously in the 5’ to 3’ direction toward
the replication fork.
8. What are the short segments of DNA synthesized on the lagging strand
called?
A. Primers
B. Exons
C. Okazaki fragments
D. Introns
Answer: C
Rationale: Okazaki fragments are small DNA pieces synthesized discontinuously on the
lagging strand away from the replication fork.
