Fundamental Molecular Biology – Exam
Questions & Answers (With Explanations)
(Part 1):
DNA Structure
Question 1
DNA nucleotides consist of:
A) Sugar + phosphate + amino acid
B) Sugar + phosphate + nitrogenous base
C) Lipid + sugar + base
D) Protein + phosphate + base
Answer: B) Sugar + phosphate + nitrogenous base
Explanation: Each nucleotide contains a deoxyribose
sugar, a phosphate group, and a nitrogenous base.
Question 2
Which bases form hydrogen bonds in DNA?
A) A–C and G–T
B) A–T and G–C
C) A–G and T–C
D) A–A and G–G
Answer: B) A–T and G–C
Explanation: Adenine pairs with thymine and guanine
pairs with cytosine through hydrogen bonds.
1
,Question 3
DNA strands are:
A) Parallel
B) Antiparallel
C) Circular
D) Identical
Answer: B) Antiparallel
Explanation: One strand runs 5'→3' while the other
runs 3'→5'.
DNA Replication
Question 4
DNA replication is:
A) Conservative
B) Semiconservative
C) Dispersive
D) Random
Answer: B) Semiconservative
Explanation: Each daughter DNA molecule contains
one original strand and one new strand.
Question 5
The enzyme that synthesizes RNA primers is:
A) Helicase
B) Primase
C) Ligase
D) Topoisomerase
2
,Answer: B) Primase
Explanation: Primase produces short RNA primers
required for DNA polymerase activity.
Question 6
DNA polymerase adds nucleotides in the:
A) 3' → 5' direction
B) 5' → 3' direction
C) Both directions
D) Random direction
Answer: B) 5' → 3' direction
Explanation: DNA polymerase extends DNA by adding
nucleotides to the 3' end.
Question 7
The leading strand is synthesized:
A) Discontinuously
B) Slowly
C) Continuously
D) Without enzymes
Answer: C) Continuously
Explanation: The leading strand is synthesized
continuously toward the replication fork.
Question 8
Okazaki fragments occur on the:
A) Leading strand
B) Lagging strand
3
, C) RNA strand
D) Template strand only
Answer: B) Lagging strand
Explanation: The lagging strand is synthesized
discontinuously forming Okazaki fragments.
Question 9
RNA primers are removed by:
A) DNA polymerase I
B) Ligase
C) Helicase
D) Primase
Answer: A) DNA polymerase I
Explanation: DNA polymerase I removes RNA primers
and replaces them with DNA.
Question 10
Replication forks form when:
A) DNA is degraded
B) DNA unwinds
C) RNA is synthesized
D) Proteins bind DNA
Answer: B) DNA unwinds
Explanation: Replication forks are created when
Helicase separates DNA strands.
4
Questions & Answers (With Explanations)
(Part 1):
DNA Structure
Question 1
DNA nucleotides consist of:
A) Sugar + phosphate + amino acid
B) Sugar + phosphate + nitrogenous base
C) Lipid + sugar + base
D) Protein + phosphate + base
Answer: B) Sugar + phosphate + nitrogenous base
Explanation: Each nucleotide contains a deoxyribose
sugar, a phosphate group, and a nitrogenous base.
Question 2
Which bases form hydrogen bonds in DNA?
A) A–C and G–T
B) A–T and G–C
C) A–G and T–C
D) A–A and G–G
Answer: B) A–T and G–C
Explanation: Adenine pairs with thymine and guanine
pairs with cytosine through hydrogen bonds.
1
,Question 3
DNA strands are:
A) Parallel
B) Antiparallel
C) Circular
D) Identical
Answer: B) Antiparallel
Explanation: One strand runs 5'→3' while the other
runs 3'→5'.
DNA Replication
Question 4
DNA replication is:
A) Conservative
B) Semiconservative
C) Dispersive
D) Random
Answer: B) Semiconservative
Explanation: Each daughter DNA molecule contains
one original strand and one new strand.
Question 5
The enzyme that synthesizes RNA primers is:
A) Helicase
B) Primase
C) Ligase
D) Topoisomerase
2
,Answer: B) Primase
Explanation: Primase produces short RNA primers
required for DNA polymerase activity.
Question 6
DNA polymerase adds nucleotides in the:
A) 3' → 5' direction
B) 5' → 3' direction
C) Both directions
D) Random direction
Answer: B) 5' → 3' direction
Explanation: DNA polymerase extends DNA by adding
nucleotides to the 3' end.
Question 7
The leading strand is synthesized:
A) Discontinuously
B) Slowly
C) Continuously
D) Without enzymes
Answer: C) Continuously
Explanation: The leading strand is synthesized
continuously toward the replication fork.
Question 8
Okazaki fragments occur on the:
A) Leading strand
B) Lagging strand
3
, C) RNA strand
D) Template strand only
Answer: B) Lagging strand
Explanation: The lagging strand is synthesized
discontinuously forming Okazaki fragments.
Question 9
RNA primers are removed by:
A) DNA polymerase I
B) Ligase
C) Helicase
D) Primase
Answer: A) DNA polymerase I
Explanation: DNA polymerase I removes RNA primers
and replaces them with DNA.
Question 10
Replication forks form when:
A) DNA is degraded
B) DNA unwinds
C) RNA is synthesized
D) Proteins bind DNA
Answer: B) DNA unwinds
Explanation: Replication forks are created when
Helicase separates DNA strands.
4
