DNA Replication MCQs : This section focuses on the "DNA Replication". These Multiple Choice Questions (MCQs) should be practiced to improve the DNA Replication skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.
Question 1
Both strands of DNA serve as templates concurrently in
A. replication
B. excision repair
C. mismatch repair
D. none of the above
Question 2
Proofreading activity to maintain the fidelity of DNA synthesis
A. occurs after the synthesis has been completed
B. is a function of the 3'-5' exonuclease activity of the DNA polymerases
C. requires the presence of an enzyme separate from the DNA polymerases
D. occurs in prokaryotes but not eukaryotes
Question 3
Which of the following repairs nicked DNA by forming a phosphodiester bond between adjacent nucleotides?
A. Helicase
B. DNA gyrase
C. Topoisomerases
D. DNA ligase
Question 4
The enzyme that catalyzes the synthesis of DNA is called
A. DNA polymerase
B. DNA gyrase
C. DNA ligase
D. helicase
Question 5
Which of the following possesses both 5'-3' and 3'-5' exonuclease activity?
A. Kornberg enzyme
B. DNA polymerase III
C. Taq DNA polymerase
D. None of these
Question 6
Which of the following statements on replication in E.coli is correct?
A. It occurs in a unidirectional manner
B. It occurs in bidirectional manner
C. Always uses T7 DNA polymerase when infected by T7 phage
D. Occurs only when λ phase has infected E. coli
Question 7
The replication of chromosomes by eukaryotes occurs in a relatively short period of time because
A. the eukaryotes have more amount of DNA for replication
B. the eukaryotic replication machinery is 1000 times faster than the prokaryotes
C. each chromosome contains multiple replicons
D. eukaryotic DNA is always single stranded
Question 8
In E.coli, which enzyme synthesizes the RNA primer for Okazaki fragments?
A. DnaA
B. DnaC
C. DnaG
D. All of the above
Question 9
During which of the following process a new copy of a DNA molecule is precisely synthesized?
A. Trasformation
B. Transcription
C. Translation
D. Replication
Question 10
DNA gyrase is inhibited by
A. tetracycline
B. nalidixic acid
C. Both A and B
D. cephalosporin
Question 11
Which of the following enzymes unwind short stretches of DNA helix immediately ahead of a replication fork?
A. DNA polymerases
B. Helicases
C. Single-stranded binding proteins
D. Topoisomerases
Question 12
During DNA replication in prokaryotes, synthesis begins on the circular chromosome
A. always at the same place
B. at any stretch of DNA that is high in AT pairs
C. randomly on the chromosome
D. at the promoter
Question 13
DNA replication rates in prokaryotes are approximately of the order of
A. 10 bases per second
B. 1,00 bases per second
C. 1,000 bases per second
D. 10,000 bases per second
Question 14
Which of the following lacks 3'-5' exonuclease activity?
A. Short fragment of DNA polymerase I
B. Taq DNA polymerase
C. T4 DNA ligase
D. All of the above
Question 15
The synthesis of DNA by DNA polymerase occurs in the
A. 3' to 5' direction
B. 5' to 5' direction
C. 5' to 3' direction
D. 3' to 3' direction
Question 16
Both strands of DNA serve as templates concurrently in
A. replication
B. excision repair
C. mismatch repair
D. none of these
Question 17
DNA gyrase is inhibited by
A. tetracycline
B. nalidixic acid
C. both (a) and (b)
D. cephalosporin
Question 18
In E.coli, which enzyme synthesizes the RNA primer for Okazaki fragments?
A. DnaA
B. DnaC
C. DnaG
D. all of these
Question 19
DNA unwinding is done by ____________
A. Ligase
B. Helicase
C. Topoisomerase
D. Hexonuclease
Question 20
Eukaryotes differ from prokaryote in mechanism of DNA replication due to ____________
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. Unidirectional rather than semi-discontinuous replication
Question 21
How many copies (approximately) of DNA polymerase III are present in a typical bacterial cell?
A. 10
B. 50
C. 100
D. 200
Question 22
How many types of replication models were considered before the semiconservative nature of DNA replication was confirmed?
A. 1
B. 2
C. 3
D. 4
Question 23
Movement of the replication fork generates ________________ in the unreplicated portion of DNA.
A. positive supercoils
B. negative supercoils
C. untranslated regions
D. amino acid substitutions
Question 24
Semi-conservative DNA replication was first demonstrated in ____________
A. Drosophila melanogaster
B. Escherichia coli
C. Streptococcus pneumonae
D. Drosophila melanogaster
Question 25
Temperature-sensitive mutants can not replicate their chromosomes at non-permissive temperatures.
A. True
B. False
Question 26
The lagging strand is synthesized discontinuously.
A. True
B. False
Question 27
What is DNA replication?
A. Conservative
B. Non-conservative
C. Semi-conservative
D. None of the mentioned
Question 28
What is the reaction in DNA replication catalyzed by DNA ligase?
A. Addition of new nucleotides to the leading strand
B. Addition of new nucleotide to the lagging strand
C. Formation of a phosphodiester bond between the 3’-OH of one Okazaki fragment and the 5’-phosphate of the next on the lagging strand
D. Base pairing of the template and the newly formed DNA strand
Question 29
When was DNA polymerase III discovered as the major enzyme behind DNA replication in bacteria?
A. 1949
B. 1959
C. 1969
D. 1989
Question 30
Which enzyme joins the Okazaki fragments into a continuous strand?
A. gyrase
B. topoisomerase
C. ligase
D. helicase
Question 31
Which enzyme removes the positive supercoils generated when the replication fork?
A. helicase
B. endonuclease
C. exonuclease
D. gyrase
Question 32
Which enzyme used to join bits of DNA?
A. DNA polymerase
B. DNA ligase
C. Endonuclease
D. Primase
Question 33
Which isotopes were used by the researchers who first confirmed the semiconservative nature of DNA replication?
A. Nitrogen
B. Carbon
C. Oxygen
D. Sulfur
Question 34
Which of the following enzyme is responsible for initiating DNA replication?
A. polymerase
B. ligase
C. primase
D. gyrase
Question 35
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
Question 36
Which of the following enzymes remove supercoiling in replicating DNA ahead of the replication fork?
A. DNA polymerases
B. Helicases
C. Primases
D. Topoisomerases
Question 37
Which of the following is true about DNA polymerase?
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
Question 38
Who made the discovery that one DNA strand is synthesized discontinuously in fragments?
A. Francis Crick
B. Reiji Okazaki
C. James Watson
D. Louis Pasteur
Question 39
Double-helix structure of DNA is discovered by___________
A. Gobind Khurana
B. Nirenberg
C. Watson and Crick
D. Darwin
Question 40
Base sequence of each parental strand considered to synthesis new complementary strand.
A. True
B. False
Question 41
How many numbers of replicon is found in E.coli?
A. Five replicon
B. Two replicon
C. Single replicon
D. Multiple replicon
Question 42
Name the protein, which is responsible for the formation of RNA primer?
A. Topoisomerase
B. Gyrase
C. Helicase
D. Primase
Question 43
Name the protein, which is used for termination of replication?
A. DnaC
B. SSB
C. Tus protein
D. DNA polymerase
Question 44
What is a mode of replication in E.coli?
A. Intermediate
B. Dispersive
C. Conservative
D. Semiconservative
Question 45
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
Question 46
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
Question 47
Which of the following protein is required for connecting Okazaki fragments?
A. Scaffold protein
B. Helicase
C. Primase
D. DNA gyrase
Question 48
Which of the following would relax negatively supercoiled DNA?
A. DNA gyrase
B. Type I topoisomerase
C. Collagen
D. Elastin