Questions on DNA Structure and Replication
20 multiple-choice questions (with five options each: A–E) on DNA Structure and Replication, followed by the answer key at the end.
Multiple-Choice Questions: DNA Structure and Replication
1. What is the shape of the DNA molecule?
A) Linear
B) Circular
C) Double helix
D) Triple helix
E) Spiral ladder
2. Which of the following is a nitrogenous base found in DNA?
A) Uracil
B) Adenine
C) Ribose
D) Phosphate
E) Histone
3. In DNA, adenine (A) pairs with:
A) Guanine
B) Uracil
C) Cytosine
D) Thymine
E) Ribose
4. The sugar present in DNA is:
A) Glucose
B) Ribose
C) Deoxyribose
D) Fructose
E) Lactose
5. Which enzyme is responsible for unzipping the DNA strand during replication?
A) DNA ligase
B) RNA polymerase
C) DNA helicase
D) DNA polymerase
E) Topoisomerase
6. What type of bond holds the two strands of DNA together?
A) Ionic bonds
B) Covalent bonds
C) Hydrogen bonds
D) Peptide bonds
E) Metallic bonds
7. Which enzyme adds new nucleotides during DNA replication?
A) DNA helicase
B) DNA ligase
C) RNA polymerase
D) DNA polymerase
E) Primase
8. Which base is not found in DNA?
A) Adenine
B) Cytosine
C) Guanine
D) Thymine
E) Uracil
9. The backbone of a DNA molecule is made of:
A) Bases and sugars
B) Phosphate and sugar
C) Sugars and amino acids
D) Phosphates and bases
E) Proteins and RNA
10. Who proposed the double helix model of DNA?
A) Hershey and Chase
B) Franklin and Chargaff
C) Watson and Crick
D) Mendel and Morgan
E) Avery and MacLeod
11. The process of copying DNA into two identical strands is called:
A) Transcription
B) Translation
C) Transformation
D) Replication
E) Duplication
12. What is the role of DNA ligase in replication?
A) Breaking hydrogen bonds
B) Adding primers
C) Sealing gaps between Okazaki fragments
D) Synthesizing new strands
E) Unwinding the helix
13. Replication of DNA is described as:
A) Conservative
B) Disruptive
C) Semi-conservative
D) Non-conservative
E) Radical
14. The lagging strand is synthesized in small segments called:
A) DNA loops
B) Introns
C) Exons
D) Okazaki fragments
E) Codons
15. Primase synthesizes:
A) DNA primers
B) RNA primers
C) DNA fragments
D) Proteins
E) mRNA
16. Which part of the nucleotide varies between A, T, G, and C?
A) Sugar
B) Phosphate group
C) Nitrogenous base
D) Ribose
E) Backbone
17. The enzyme that prevents overwinding ahead of the replication fork is:
A) Helicase
B) Ligase
C) Primase
D) Topoisomerase
E) Polymerase
18. Which direction does DNA polymerase synthesize the new strand?
A) 3’ to 3’
B) 5’ to 5’
C) 3’ to 5’
D) 5’ to 3’
E) Random direction
19. The point where the two strands of DNA are separated for replication is called:
A) Codon
B) Chromatid
C) Replication fork
D) Ribosome
E) Promoter
20. If one strand of DNA has the sequence 5’-ATCGTACG-3’, what is the complementary strand?
A) 5’-CGTACGAT-3’
B) 3’-TAGCATGC-5’
C) 5’-TAGCATGC-3’
D) 3’-ATCGTACG-5’
E) 3’-GCATGCTA-5’
Answer Key:
1. C
2. B
3. D
4. C
5. C
6. C
7. D
8. E
9. B
10. C
11. D
12. C
13. C
14. D
15. B
16. C
17. D
18. D
19. C
20. B
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