CHEM 210 Module 6 Exam: Biochemistry - Genetics and Molecular
Biology 2026 Geneva College
1. Which of the following nitrogenous bases is found in RNA but not in DNA?
A. Adenine
B. Thymine
C. Cytosine
D. Uracil
Answer: D
Rationale: RNA uses Uracil instead of Thymine, which is found in DNA.
2. What type of bond connects the sugar-phosphate backbone of a DNA strand?
A. Hydrogen bond
B. Ionic bond
C. Peptide bond
D. Phosphodiester bond
Answer: D
Rationale: Phosphodiester bonds link the 3’ carbon of one sugar molecule to the 5’ carbon
of another.
,3. In the 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 share three hydrogen bonds, making them slightly more stable than
A-T pairs, which share two.
4. Which enzyme is responsible for relieving torsional strain (supercoiling)
ahead of the replication fork?
A. DNA Helicase
B. DNA Ligase
C. Topoisomerase
D. Primase
Answer: C
Rationale: Topoisomerase (such as DNA gyrase) cuts and reseals DNA to prevent
overwinding during replication.
5. Replication of DNA is described as ‘semi-conservative’. What does this mean?
A. The entire original double helix is conserved.
B. Each new double helix consists of one old strand and one new strand.
C. Parts of all four strands are mixed together randomly.
D. Only the exons are conserved.
Answer: B
Rationale: Semi-conservative replication means each daughter molecule contains one
parental strand and one newly synthesized strand.
, 6. In which direction does DNA Polymerase synthesize a new DNA strand?
A. 3’ to 5’
B. N-terminus to C-terminus
C. 5’ to 3’
D. Bidirectionally from the center
Answer: C
Rationale: DNA Polymerase adds nucleotides only to the 3’ end of a growing strand,
meaning synthesis occurs in the 5’ to 3’ direction.
7. What is the function of the enzyme Helicase?
A. To synthesize RNA primers
B. To join Okazaki fragments
C. To repair mismatched bases
D. To unwind the DNA double helix
Answer: D
Rationale: Helicase breaks the hydrogen bonds between bases to separate the two strands
of DNA.
8. Okazaki fragments are found on which of the following?
A. The leading strand
B. The lagging strand
C. The mRNA transcript
D. The ribosome
Answer: B
Rationale: Because DNA synthesis is 5’ to 3’, the lagging strand is synthesized
discontinuously in short segments called Okazaki fragments.
Biology 2026 Geneva College
1. Which of the following nitrogenous bases is found in RNA but not in DNA?
A. Adenine
B. Thymine
C. Cytosine
D. Uracil
Answer: D
Rationale: RNA uses Uracil instead of Thymine, which is found in DNA.
2. What type of bond connects the sugar-phosphate backbone of a DNA strand?
A. Hydrogen bond
B. Ionic bond
C. Peptide bond
D. Phosphodiester bond
Answer: D
Rationale: Phosphodiester bonds link the 3’ carbon of one sugar molecule to the 5’ carbon
of another.
,3. In the 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 share three hydrogen bonds, making them slightly more stable than
A-T pairs, which share two.
4. Which enzyme is responsible for relieving torsional strain (supercoiling)
ahead of the replication fork?
A. DNA Helicase
B. DNA Ligase
C. Topoisomerase
D. Primase
Answer: C
Rationale: Topoisomerase (such as DNA gyrase) cuts and reseals DNA to prevent
overwinding during replication.
5. Replication of DNA is described as ‘semi-conservative’. What does this mean?
A. The entire original double helix is conserved.
B. Each new double helix consists of one old strand and one new strand.
C. Parts of all four strands are mixed together randomly.
D. Only the exons are conserved.
Answer: B
Rationale: Semi-conservative replication means each daughter molecule contains one
parental strand and one newly synthesized strand.
, 6. In which direction does DNA Polymerase synthesize a new DNA strand?
A. 3’ to 5’
B. N-terminus to C-terminus
C. 5’ to 3’
D. Bidirectionally from the center
Answer: C
Rationale: DNA Polymerase adds nucleotides only to the 3’ end of a growing strand,
meaning synthesis occurs in the 5’ to 3’ direction.
7. What is the function of the enzyme Helicase?
A. To synthesize RNA primers
B. To join Okazaki fragments
C. To repair mismatched bases
D. To unwind the DNA double helix
Answer: D
Rationale: Helicase breaks the hydrogen bonds between bases to separate the two strands
of DNA.
8. Okazaki fragments are found on which of the following?
A. The leading strand
B. The lagging strand
C. The mRNA transcript
D. The ribosome
Answer: B
Rationale: Because DNA synthesis is 5’ to 3’, the lagging strand is synthesized
discontinuously in short segments called Okazaki fragments.
