MCQ on DNA Replication with Answers :
DNA Replication key Points :
- In Drosophila melanogaster the Semi-conservative DNA replication was first demonstrated.
- E.coli bacteria is used for DNA replication studies.
- DNA replication is bidirectional and anti-parallel.
- The Chargaff rules state that the number of purines and pyrimidines are equal (A+G = T + C) in any double-stranded DNA molecules. Watson and Crick later solved the structure of DNA and nitrogen base pairings.
- Particular site at which DNA replication starts is called Origin of replication.
- Helicase enzymes separates the two strands of DNA during replication.
- Topoisomerase enzymes remove supercoiling in replicating DNA ahead of the replication fork.
- 3’ to 5’ exonuclease activity is required for proofreading during DNA replication by DNA polymerase III.
- Termination of replication is triggered by tus Protein.
- DNA polymerase synthesizes DNA in 5’-3’ direction.
- The fragments of DNA are joined together by Ligase enzymes.
- In some viruses DNA is synthesized from RNA by the reverse transcriptase enzyme.
Multiple Choice Questions on DNA Replication :
1. In which of the following organisms the Semi-conservative DNA replication was first demonstrated____________
(a) Drosophila melanogaster
(b) Escherichia coli
(c) Streptococcus pneumonae
(d) Drosophila melanogaster
Answer: A
2. Which of the following bacteria is used for DNA replication studies?
(a) Neurospora crassa
(b) Drosophila melanogaster
(c) Escherichia coli
(d) Pneumococcus
Answer: C
3. DNA replication is bidirectional and anti-parallel. Which of the statement is FALSE regarding the DNA replication?
(a) The DNA synthesis i.e. addition of nucleotide occurs from 5'-3' position
(b) The DNA synthesis is semi-continuous with continuous leading strand and discontinuous lagging strand.
(c) The synthesis of leading and lagging strands occurs simultaneously
(d) None of the Above
Answer: D
4. Which of the followings are the characteristic feature of DNA replication________
(a) DNA replication requires Semi conservative and Bidirectional
(b) DNA replication requires short RNA primers
(c) DNA replication is a highly accurate process
(d) All of the Above
Answer: D
5. The Chargaff rules state that the number of purines and pyrimidines are equal (A+G = T + C) in any double-stranded DNA molecules. Watson and Crick later solved the structure of DNA and nitrogen base pairings. Which of the following base pairing rule is true______
(a) Adenine pairs with Guanine and Thymine pairs with Cytosine
(b) Adenine pairs with Thymine and Guanine pairs with Cytosine
(c) Adenine pairs with Cytosine and Guanine pairs with Thymine
(d) DNA base pairing is nonspecific
Answer: B
6. Eukaryotic Organisms differ from prokaryotic organisms in mechanism of DNA replication due to the____________
(a) Use of DNA primer rather than RNA primer
(b) Different enzyme for synthesis of lagging and leading strand
(c) Discontinuous rather than semi-discontinuous replication
(d) None of the above
Answer: C
7. Which of the following protein is required for connecting Okazaki fragments?
(a) Scaffold protein
(b) Helicase
(c) Primase
(d) DNA gyrase
Answer: D
8. Which of the following protein does not involve in the initiation of replication?
(a) DnaA
(b) SSB (Single strand binding protein)
(c) DnaB
(d) DnaF
Answer: D
9. What is the origin of replication?
(a) Particular site at which DNA replication starts
(b) Site which prevents initiation
(c) Random location on the DNA
(d) Site at which replication terminated
Answer: A
10. Which of the following enzymes separates the two strands of DNA during replication?
(a) Gyrase
(b) Topoisomerase
(c) Helicase
(d) DNA polymerase
Answer: C
11. Which of the following enzymes remove supercoiling in replicating DNA ahead of the replication fork?
(a) DNA polymerases
(b) Helicases
(c) Primases
(d) Topoisomerases
Answer: D
12. Name the protein, which is used for termination of replication?
(a) Collagen
(b) SSB
(c) Tus protein
(d) DNA polymerase
Answer: C
13. DNA replication is__________
(a) conservative
(b) conservative and discontinuous
(c) semi-conservative and discontinuous
(d) semi-conservative and semi-discontinuous
Answer: D
14. Which of the following reactions is required for proofreading during DNA replication by DNA polymerase III?
(a) 5’ to 3’ exonuclease activity
(b) 3’ to 5’ exonuclease activity
(c) 3’ to 5’ endonuclease activity
(d) 5’ to 3’ endonuclease activity
Answer: B
15. Termination of replication is triggered by_________
(a) DNA polymerase
(b) Helicase
(c) SSB
(d) Tus protein
Answer: D
16. DNA unwinding is done by____________
(a) Ligase
(b) Helicase
(c) Topoisomerase
(d) Hexonuclease
Answer: B
17. DNA polymerase synthesizes__________
(a) DNA in 5’-3’ direction
(b) DNA in 3’-5’ direction
(c) mRNA in 3’-5’ direction
(d) mRNA in 5’-3’ direction
Answer: A
18. Which of the following statement is true about DNA polymerase enzyme?
(a) It can synthesize DNA in the 5’ to 3’ direction
(b) It can synthesize DNA in the 3’ to 5’ direction
(c) It can synthesize mRNA in the 3’ to 5’ direction
(d) It can synthesize mRNA in the 5’ to 3’ direction
Answer: A
19. What is a mode of replication in E.coli?
(a) Intermediate
(b) Dispersive
(c) Conservative
(d) Semiconservative
Answer: D
20. The fragments of DNA are joined together by which of the following enzymes?
(a) Endonuclease
(b) DNA polymerase
(c) Primase
(d) Ligase
Answer: D
21. Name the protein, which is responsible for the formation of RNA primer?
(a) Topoisomerase
(b) Gyrase
(c) Helicase
(d) Primase
Answer: D
22. How many numbers of replicon is found in E.coli?
(a) Five replicon
(b) Two replicon
(c) Single replicon
(d) Multiple replicon
Answer: C
23. How many numbers of replicon is found in Eukaryotes?
(a) Five replicon
(b) Two replicon
(c) Single replicon
(d) Multiple replicon
Answer : D
24. Which of the following enzymes adds DNA to the ends of chromosomes to avoid loss of genetic material with duplication?
(a) Polymerase
(b) Helicase
(c) Telomerase
(d) Primase
Answer: C
25. Which of the following structures indicates where DNA replication begins?
(a) Replication fork
(b) Helicase
(c) Origin of replication
(d) DNA polymerase III
Answer: C
26. What is the role of helicase?
(a) Nicks the DNA backbone to relieve supercoils
(b) Unwinds DNA template at the replication fork
(c) Facilitates formation of phosphodiester bonds
(d) Prevents DNA strands from reannealing
Answer: B
27. In eukaryotes, which of the following DNA polymerase is required for mitochondrial DNA replication?
(a) DNA Polymerase alpha
(b) DNA Polymerase beta
(c) DNA Polymerase gamma
(d) DNA Polymerase delta
Answer: C
28. Which of the following enzymes is the principal replication enzyme in E. coli?
(a) DNA polymerase I
(b) DNA polymerase II
(c) DNA polymerase III
(d) None of the mentioned
Answer: C
29. In some viruses DNA is synthesized from RNA by the enzyme_____________
(a) DNA synthetase
(b) DNA polymerase
(c) Reverse transcriptase
(d) RNA Polymerase
Answer: C
30. During DNA replication, single-stranded DNA is kept from reannealing due to the function of__________
(a) Histones
(b) Single-strand binding proteins
(c) Helicase
(d) DNA topoisomerase
Answer: B
31. What 3' functional group must be free in order to add the next nucleotide during DNA synthesis?
(a) Amine
(b) Phosphate
(c) Carboxylic acid
(d) Hydroxyl
Answer: D
32. Magnesium is a necessary component of DNA polymerization, but is not found in the DNA molecule. What is the purpose of magnesium in the polymerization of DNA?
(a) It binds to the two leaving groups during the DNA polymerization reaction
(b) It is a cofactor for DNA polymerase III
(c) It binds nucleotides in the cytosol and helps import them into the nucleus
(d) None of these answers are correct
Answer: A
33. DNA polymerase III holoenzyme possesses the________
(a) polymerase activity only
(b) 3’→ 5’ endonuclease activity
(c) 3’→ 5’ exonuclease activity and polymerase activities
(d) 5’→ 3’ exonuclease activity
Answer: C
34. Which enzyme is responsible for removing the RNA primers added during DNA replication?
(a) Primase
(b) DNA ligase
(c) DNA polymerase I
(d) DNA polymerase III
Answer: C
35. What is the role of topoisomerases in eukaryotic DNA replication?
(a) Topoisomerise enzymes cut, uncoil and reseal the double stranded DNA
(b) Topoisomerise enzymes bind to the origin of replication sites within double stranded DNA
(c) Topoisomerise enzymes open up the double stranded DNA at the replication fork
(d) Topoisomerise enzymes join the Okazaki fragments together with phosphodietster bonds
Answer: A
