Tag: pcr

Questions Related to pcr

Enzyme' Taq polymerase' used in PCR, has been isolated from bacterium _________________.

bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

  1. Agrobacterium tumefaciens

  2. Thermus aquaticus

  3. Streptomyces albus

  4. Escherichia coli

Show answer
Correct Option: B
Explanation:

The final step of PCR is the extension, wherein Taq DNA polymerase is isolated from a thermophilic bacterium Thermus aquaticus.

The polymerase chain reaction is a technique used for ____________.

bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

  1. Amplification of DNA

  2. Amplification of enzymes

  3. Amplification of proteins

  4. All of these

Show answer
Correct Option: A
Explanation:

Polymerase chain reaction is a technique used for amplification of DNA fragments. Its amplification cycle involve three steps - denaturation, annealing and polymerisation which are repeated for 'n', cycles.

Which of the following statements are correct for the enzyme Taq polymerase?


(i) It remains active during the high temperature-induced denaturation of dsDNA.

(ii) It requires primers for carrying out the process of polymerisation.
(iii) It synthesizes the RNA region between the primers, using $dNTPs$ and $Mg^{2+}$ _______________.

bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

  1. (i) and (ii)

  2. (ii) and (iii)

  3. (i), (ii) and (iii)

  4. None of these

Show answer
Correct Option: A
Explanation:

The final step of PCR is the extension, wherein Taq DNA polymerase (isolated from a thermophilic bacterium Thermus aquaticus) synthesizes the DNA region between the primers, using dNTPs (deoxynucleoside triphosphates) and $Mg^{2+}$. The primers are extended towards each other so that the DNA segment lying between the two primers is copied. The optimum temperature for this polymerisation step is $72^o$$C$. Taq polymerase remains active during high temperature-induced denaturation of double-stranded DNA.

Process used for amplification or multiplication of DNA in DNA fingerprinting is

bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

  1. Polymerase chain reaction

  2. Southern blotting

  3. Northern blotting

  4. None of these

Show answer
Correct Option: A
Explanation:

Process used for amplification or multiplication of DNA in DNA fingerprinting is Polymerase chain reaction (PCR) .It is done in invitro system.

So, the correct option is 'Option A' . 

Primers are

bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

  1. Chemically synthesised oligonucleotides that are complementary to the regions of DNA

  2. Chemically synthesised oligonucleotides that are not complementary to the regions of DNA

  3. Chemically synthesised, autonomously replicating circular DNA molecules

  4. Specific sequences present on recombinant DNA

Show answer
Correct Option: A
Explanation:
Primers are small, chemically synthesised oligonucleotides that are complementary to the sequences, present at 3' end of the template DNA. They hybridise to the target DNA region, one to each strand of the double helix. These primers are oriented with their ends facing each other allowing synthesis of the DNA towards one another.
So, the correct answer is 'Chemically synthesised oligonucleotides that are complementary to the regions of DNA'.

Given table gives an account of differences between PCR and gene cloning. Which of the, following points shows the incorrect difference?

  Parameter PCR Gene cloning
1 Efficient More Less
2 Apparatus Requirement DNA Restriction enzyme, ligase, vector, bacterial cell
3 Manipulation In vitro In vitro and in vivo
4 Cost More Less
5 Automation Yes No
6 Error probability Less More
7 Time for a typical experiment 2-4 days 4 hours
8 Application More Less


bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

  1. 1 and 3

  2. 4 and 6

  3. 4 and 7

  4. 4, 7 and 8

Show answer
Correct Option: C
Explanation:

The cost of gene cloning is far more than PCR because gene cloning requires many intricate steps. PCR takes less than 4 hours while gene cloning can take days.

In a polymerase chain reaction, temperature required for the steps (i) Denaturation,(ii) Annealing, and (iii) Extension are respectively.

bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

  1. (i) $94^o$$C$ (ii) $40^o$$C$ (iii) $72^o$$C$

  2. (i) $40^o$$C$ (ii) $72^o$$C$ (iii) $94^o$$C$

  3. (i) $94^o$$C$ (ii) $72^o$$C$ (iii) $40^o$$C$

  4. (i) $72^o$$C$ (ii) $94^o$$C$ (iii) $40^o$$C$

Show answer
Correct Option: A
Explanation:
  • At the start of PCR, the DNA from which a segment is to be amplified, an excess of the two primer molecules, the four deoxynucleoside triphosphates and the DNA polymerase are mixed in the reaction mixture that has appropriate quantities of $Mg^{2+}$. 
  • The reaction mixture is first heated to a temperature between $90-$$98^oC$ (commonly $94^oC$) that ensures DNA denaturation. Every single strand of the target DNA then acts as a template for DNA synthesis. This is the denaturation step. The duration of this step in the first cycle of PCR is usually 2 min at  $94^oC$. 
  • The mixture is now cooled to a temperature (generally $40-60^oC$) that permits annealing of the primer to the complementary sequences in the DNA. This step is called annealing. The duration of the annealing step is usually 1 min.
  • The primers are extended towards each other so that the DNA segment lying between the two primers is copied, this is ensured by employing primers complementary to the 3': ends of the segment to be amplified. The duration of primer extension is usually 2 min at $72^oC$. 

In addition to Taq polymerase enzyme which other thermostable DNA polymerases have been isolated to be used in polymerase chain Reaction (PCR)?

bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

  1. Pfu polymerase isolated from Pyrococcus furiosus

  2. Tli polymerase (vent polymerase) isolated from Thermococcus litoralis

  3. Both (a) and (b)

  4. None of these

Show answer
Correct Option: C
Explanation:

In addition to Tag DNA polymerase, Pfu polymerase and Tli polymerase have been isolated which are also thermostable. Pfu polymerase is isolated from Pyrococcus furiosus. Tli (vent) polymerase is isolated from Thermococcus litoralis.

Which one of the following is not a correct match?

bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

  1. Tumor Inducing - Ti plasmid

  2. DNA probe - Identifies the desired DNA fragment

  3. PCR - DNA staining

  4. Agarose - Sea weeds

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Correct Option: C

The correct sequence of different steps of polymerase chain reaction is

bio-chemistry applications of biotechnology pcr cutting, insertion and ligation of dna gene cloning procedure biotechnological regulations asexual modes of reproduction

  1. Annealing denaturation extension

  2. Denaturation extension annealing

  3. Denaturation annealing extension

  4. Extension denaturation annealing

Show answer
Correct Option: C
Explanation:
Polymerase chain reaction is a technique used to replicate a fragment of DNA so as to produce many copies of a particular DNA sequence. A single PCR amplification cycle involves three basic steps: denaturation, annealing and extension (polymerisation).
So, the correct answer is 'Denaturation annealing extension'.