PCR - 聚合酶链式反应

The goal of PCR, Polymerase Chain Reaction is to amplify a genetic sequence. In this example, a gene of interest will be amplified from purified DNA. In order to perform the amplification, a polymerase is required to synthesize the new DNA.

A primer, a short piece of single stranded DNA that shares homology to the gene of interest is also needed. Finally, single nucleotides called Deoxynucleoside triphosphates or dNTPs are used to make the new strand. The first step in PCR is to heat the mixture which denatures the DNA.

Next, the reaction is cooled and the primers will anneal to their homologous region. Once bound the reaction is heated to an optimal temperature for the polymerase. The polymerase then recognizes the primer DNA complex and begins synthesis of the new strand using the dNTPs in the solution.

The reaction is then heated and proceeds as described across additional cycles. Following the third cycle, there are eight total copies of the gene. After the fourth cycle, 16 copies.

And fifth cycle, 32 copies. The number of cycles will continue to grow exponentially. After 30 cycles, there are just over one billion copies.