DNA Quiz | DNA Objective Type Questions & Answers

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Questions
21 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

Answer: DNA ligase
22 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 ? phase has infected E. coli

Answer: It occurs in bidirectional manner
23 DNA gyrase is inhibited by
A tetracycline
B nalidixic acid
C both (a) and (b)
D cephalosporin

Answer: nalidixic acid
24 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

Answer: 1,000 bases per second
25 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

Answer: 5′ to 3′ direction
26 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

Answer: always at the same place
27 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

Answer: All of the above
28 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

Answer: Helicases
29 During which of the following process a new copy of a DNA molecule is precisely synthesized?
A Trasformation
B Transcription
C Translation
D Replication

Answer: Replication
30 In E.coli, which enzyme synthesizes the RNA primer for Okazaki fragments?
A DnaA
B DnaC
C DnaG
D all of these

Answer: DnaG
31 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

Answer: each chromosome contains multiple replicons
32 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

Answer: Kornberg enzyme
33 The enzyme that catalyzes the synthesis of DNA is called
A DNA polymerase
B DNA gyrase
C DNA ligase
D helicase

Answer: DNA polymerase
34 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

Answer: is a function of the 3′-5′ exonuclease activity of the DNA polymerases
35 The enzyme used to join bits of DNA is
A DNA polymerase
B DNA ligase
C Endonuclease
D Primase

Answer: DNA ligase
36 DNA unwinding is done by
A Ligase
B Helicase
C Topoisomerase
D Hexonuclease

Answer: Helicase
37 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: 3’ to 5’ exonuclease activity
38 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

Answer: It can synthesize DNA in the 5’ to 3’ direction
39 Semi-conservative DNA replication was first demonstrated in
A Drosophila melanogaster
B Escherichia coli
C Streptococcus pneumonae
D Drosophila melanogaster

Answer: Drosophila melanogaster
40 Levene investigated and found that the nucleic acid is composed of poly-nucleotides and each nucleotide is composed of one base, a sugar molecule and a phosphate. This was performed on the genome of________________
A Bacteria
B Fungi
C WBCs
D Yeast

Answer: Yeast

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