How is the amplification of a gene sample of interest carried out using PCR ?

Explanation

(i) The polymerase chain reaction (PCR) is an in virto amplification technique used for synthesising multiple identical copies (billions) of DNA of interest.
(ii) Denaturation, renaturation or primer annealing and synthesis or primer extension, are the three steps involved in PCR.
(iii) The double stranded DNA of interset is denaturated to separate into two individual strands by high temperautre. This is called denaturation.
(iv) Each strand is allowed to hybridize with a primer ( renaturation or primer annealing). The primer template is used to synthesize DNA by using Taq-DNA polymerase.
(v) During denaturation the reaction mixutre is heated to `95^@ C` for a short time to denautre the target DNA into signle strands that will act as template for DNA synthesis.
(vi) Annealing is done by rapid cooling of the mixutre , allowing the primers to bind to the sequences on each of the two strands flanking the target DNA .
(vii) During primer extension or synthesis the temperature of the mixture is increased to `75^@C` for a sufficient period of time to allow Taq DNA polymerase to extend each primer by copying the single stranded template. At the end of incubation both single template strands will be made partially double stranded. The new strand of each double stranded DNA extends to a variable distance downstream.
(viii) These steps are repeated again and again to gererate multiple forms of the desired DNA. This process is also called DNA amplification.