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Free download in PDF DNA Objective Type Questions & Answers for competitive exams. These objective type questions are very important for competitive exams like NEET, AIIMS, JIPMER etc. These short solved questions or quizzes are provided by Gkseries.
(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
(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
(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
(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
(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
(30)
In E.coli, which enzyme synthesizes the RNA primer for Okazaki fragments?
[A]
DnaA
[B]
DnaC
[C]
DnaG
[D]
all of these
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
33
The enzyme that catalyzes the synthesis of DNA is called
[A]
DNA polymerase
[B]
DNA gyrase
[C]
DNA ligase
[D]
helicase
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
36
DNA unwinding is done by
[A]
Ligase
[B]
Helicase
[C]
Topoisomerase
[D]
Hexonuclease
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
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