CHEM 219 MODULE 6: NUCLEIC ACIDS
AND GENETICS QUESTIONS WITH
CORRECT ANSWERS 2026/2027 UPDATE.
JUST RELEASED
1. Which structural feature distinguishes a ribose sugar from a deoxyribose sugar at the
molecular level?
A. The presence of a phosphate group at the C5 position.
B. The type of nitrogenous base attached to the C1 position.
C. The presence of a hydroxyl group at the C2 position.
D. The presence of a double bond within the pentose ring.
Answer: C
Conceptual Explanation: Ribose contains a hydroxyl group (-OH) at the C2 position,
whereas deoxyribose has a hydrogen atom (-H) at that same position, which makes DNA
more stable than RNA.
2. In a double-stranded DNA molecule, if the content of Cytosine is 18%, what is the expected
percentage of Adenine?
A. 18%
B. 32%
,C. 36%
D. 64%
Answer: B
Conceptual Explanation: According to Chargaff’s rules, G=C and A=T. If C=18%, then
G=18%. Total G+C=36%. Remaining A+T=64%. Therefore, A=32%.
3. Which enzyme is responsible for relieving torsional strain (supercoiling) ahead of the
replication fork?
A. Topoisomerase (DNA Gyrase)
B. DNA Polymerase III
C. Helicase
D. Single-Strand Binding Proteins
Answer: A
Conceptual Explanation: Topoisomerases cut and reseal the DNA backbone to relieve the
tension caused by the unwinding of the double helix by helicase.
4. Which of the following statements best describes the mechanism of DNA Polymerase III?
A. It requires a free 3’-OH group to add new nucleotides.
B. It synthesizes DNA in the 3’ to 5’ direction.
C. It can initiate DNA synthesis de novo without a primer.
, D. It removes RNA primers via 5’ to 3’ exonuclease activity.
Answer: A
Conceptual Explanation: DNA Polymerase III requires a primer with a free 3’-OH group to
catalyze the formation of a phosphodiester bond with an incoming dNTP.
5. What is the primary function of the Okazaki fragments during DNA replication?
A. To provide a template for RNA synthesis.
B. To allow for the synthesis of the lagging strand in the 5’ to 3’ direction.
C. To facilitate the synthesis of the leading strand.
D. To terminate replication at the telomeres.
Answer: B
Conceptual Explanation: Since DNA polymerase only works 5’ to 3’, the lagging strand is
synthesized discontinuously in short segments called Okazaki fragments.
6. Which bond connects the 5’ phosphate group of one nucleotide to the 3’ hydroxyl group of
the adjacent nucleotide?
A. Phosphodiester bond
B. Glycosidic bond
C. Hydrogen bond
D. Peptide bond
AND GENETICS QUESTIONS WITH
CORRECT ANSWERS 2026/2027 UPDATE.
JUST RELEASED
1. Which structural feature distinguishes a ribose sugar from a deoxyribose sugar at the
molecular level?
A. The presence of a phosphate group at the C5 position.
B. The type of nitrogenous base attached to the C1 position.
C. The presence of a hydroxyl group at the C2 position.
D. The presence of a double bond within the pentose ring.
Answer: C
Conceptual Explanation: Ribose contains a hydroxyl group (-OH) at the C2 position,
whereas deoxyribose has a hydrogen atom (-H) at that same position, which makes DNA
more stable than RNA.
2. In a double-stranded DNA molecule, if the content of Cytosine is 18%, what is the expected
percentage of Adenine?
A. 18%
B. 32%
,C. 36%
D. 64%
Answer: B
Conceptual Explanation: According to Chargaff’s rules, G=C and A=T. If C=18%, then
G=18%. Total G+C=36%. Remaining A+T=64%. Therefore, A=32%.
3. Which enzyme is responsible for relieving torsional strain (supercoiling) ahead of the
replication fork?
A. Topoisomerase (DNA Gyrase)
B. DNA Polymerase III
C. Helicase
D. Single-Strand Binding Proteins
Answer: A
Conceptual Explanation: Topoisomerases cut and reseal the DNA backbone to relieve the
tension caused by the unwinding of the double helix by helicase.
4. Which of the following statements best describes the mechanism of DNA Polymerase III?
A. It requires a free 3’-OH group to add new nucleotides.
B. It synthesizes DNA in the 3’ to 5’ direction.
C. It can initiate DNA synthesis de novo without a primer.
, D. It removes RNA primers via 5’ to 3’ exonuclease activity.
Answer: A
Conceptual Explanation: DNA Polymerase III requires a primer with a free 3’-OH group to
catalyze the formation of a phosphodiester bond with an incoming dNTP.
5. What is the primary function of the Okazaki fragments during DNA replication?
A. To provide a template for RNA synthesis.
B. To allow for the synthesis of the lagging strand in the 5’ to 3’ direction.
C. To facilitate the synthesis of the leading strand.
D. To terminate replication at the telomeres.
Answer: B
Conceptual Explanation: Since DNA polymerase only works 5’ to 3’, the lagging strand is
synthesized discontinuously in short segments called Okazaki fragments.
6. Which bond connects the 5’ phosphate group of one nucleotide to the 3’ hydroxyl group of
the adjacent nucleotide?
A. Phosphodiester bond
B. Glycosidic bond
C. Hydrogen bond
D. Peptide bond
