NEET Zoology Biotechnology Principles and Processes Questions Solved


Explain the three steps involved in each cycle of polymerase chain reaction.


Three steps of polymerase chain reaction are denaturation, annealing and extension of


(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 


(ii) Annealing: The two sets of primers (small chemical synthesized oligonucleoids

that are complementary to the regions of DNA) undergo biochemical process of 

annealing at an optimum temperature of 

(iii) Extension: The enzyme DNA polymerase extends the primers using the nucleoid 

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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