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Question
The Polymerase Chain Reaction (PCR) is a technique that is used for _______i______ of specific DNA sequence using ______ii________.
The Polymerase Chain Reaction (PCR) is a technique that is used for _______i______ of specific DNA sequence using ______ii________.
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Solution
The correct option is B i - in vitro replication,
ii - thermostable DNA polymerase
Polymerase Chain Reaction (PCR) is a technique which was developed by Kary Mullis.
It is used for in vitro replication of specific DNA sequences using thermostable DNA polymerase (Taq polymerase).
It is a technique used in molecular biology to create several copies of a certain DNA segment.
There are 3 steps involved:
Denaturation: Separation of the two strands of double stranded DNA by application of heat at 96°C.
Annealing: Hybridisation of two primers with specific sequences of each of the strands of the DNA. This process is carried out at 55-65°C.
Extension: Taq DNA polymerase synthesises DNA by adding dNTPs to the free ends of the two primers - forward and reverse.
The extension of DNA is carried out at 72°C. This helps in synthesizing complementary strands. Taq polymerase attaches to the primer and adds DNA bases to the 3’ end of the primer. This elongates the DNA in the 5’ to 3’ direction.
The Taq polymerase is purified from Thermus aquaticus, a bacteria which can survive at very high temperatures. This provides an additional feature to Taq polymerase. In addition to adding deoxynucleotides, it does not get denatured at high temperatures during the denaturation step of PCR. Any other thermolabile DNA polymerase would get denatured at higher temperatures used during steps of PCR.
In vitro refers to the technique of performing a given procedure in a controlled environment outside of a living organism.
In vivo are those in which the effects of various biological entities are tested on living organisms or cells, usually animals, including humans, and plants and PCR is not conducted under in vivo conditions.
The in vivo synthesis of mRNA is the process of transcription that occurs in various organisms.
The polymerase chain reaction cannot be used for the synthesis of mRNA. The PCR process is used to amplify short segments of a DNA molecule.
ii - thermostable DNA polymerase
Polymerase Chain Reaction (PCR) is a technique which was developed by Kary Mullis.
It is used for in vitro replication of specific DNA sequences using thermostable DNA polymerase (Taq polymerase).
It is a technique used in molecular biology to create several copies of a certain DNA segment.
There are 3 steps involved:
Denaturation: Separation of the two strands of double stranded DNA by application of heat at 96°C.
Annealing: Hybridisation of two primers with specific sequences of each of the strands of the DNA. This process is carried out at 55-65°C.
Extension: Taq DNA polymerase synthesises DNA by adding dNTPs to the free ends of the two primers - forward and reverse.
The extension of DNA is carried out at 72°C. This helps in synthesizing complementary strands. Taq polymerase attaches to the primer and adds DNA bases to the 3’ end of the primer. This elongates the DNA in the 5’ to 3’ direction.
The Taq polymerase is purified from Thermus aquaticus, a bacteria which can survive at very high temperatures. This provides an additional feature to Taq polymerase. In addition to adding deoxynucleotides, it does not get denatured at high temperatures during the denaturation step of PCR. Any other thermolabile DNA polymerase would get denatured at higher temperatures used during steps of PCR.
In vitro refers to the technique of performing a given procedure in a controlled environment outside of a living organism.
In vivo are those in which the effects of various biological entities are tested on living organisms or cells, usually animals, including humans, and plants and PCR is not conducted under in vivo conditions.
The in vivo synthesis of mRNA is the process of transcription that occurs in various organisms.
The polymerase chain reaction cannot be used for the synthesis of mRNA. The PCR process is used to amplify short segments of a DNA molecule.
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