NEET Zoology Biotechnology Principles and Processes Questions Solved


Explain in sequence the process of amplification of a gene of interest using polymerase chain reaction.    (3 marks)


                     Polymerase Chain Reaction (PCR) : Each cycle has three steps :

      (i) Denaturation;      (ii) Primer annealing;     and     (iii) Extension of primers



PCR stands for polymerase Chain Reaction. In this reaction multiple copies  of the gene of interest are synthesised in vitro under three steps:

 (i) Denaturation: In this double stranded DNA is converted to single stranded, This is often

      achieved by heating or alkaline conditions. This is called melting of DNA.

(ii) Annealing: The two sets of primers (small chemical synthesized oligonucleotides that are

     complementary to the regoins of DNA) undergo biochemical process of annealing at an

     optimum temperature of 40°C-65°C.

(iii) Extension: The enzyme DNA polymerase extends the primers using the nucleotide provided in

      the reaction and the genomic DNA as template. If the process of replication of DNA is

      repeated many times, the segment of DNA can be amplified to approximately billion times.

      Such repeated amplification is achieved by the use of a thermostable DNA polymerase and

      the amplified fragment if desired can be used to ligate with a vector for further cloning.

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