Polymerase chain reaction (PCR) is a molecular biology technique used to amplify specific DNA fragments. It can be regarded as a special kind of DNA replication in vitro.

Template DNA, primers, ATP, thermostable DNA polymerase (Taq enzyme) and free deoxynucleotides are needed. It uses the principle of DNA double-stranded replication to copy the nucleotide sequence of the gene continuously, so that its number increases exponentially. (Double-stranded DNA can be denatured and unwound into single strand under the action of various enzymes, and copied to the same bimolecular mussel with the participation of DNA polymerase according to the principle of base complementary pairing. )

PCR consists of three basic reaction steps: denaturation-annealing-extension:

① denaturation of template DNA: heating the template DNA to 90℃~95℃ to melt it;

(2) annealing (renaturation) of the template DNA and the primer: cooling to 55-60 DEG C, and combining the primer with the complementary DNA strand;

③ Primer extension: heating to 70℃~75℃, Taq enzyme synthesizes complementary strand from primer.

The number of copies per cycle is doubled.

The above process can be completed automatically in PCR amplifier.

This is all the requirements of high school.