PCR also known as polymerase chain reaction, it was developed by Kary Mullis in 1983 in order to magnify small segments of DNA. PCR is a technique used to produce millions of copies of a particular DNA sequence in less amount of time than previous methods. It became important in the identification of bacteria and virus, diagnosis of disease, genetic manipulation, forensic science, cloning, and in other fields. PCR takes advantage of different temperatures while it mimics the natural process of DNA replication, its main components are two primers, segments of single DNA built in laboratories that are complementary to the DNA that is going to be copied; DNA polymerase, which synthesize the DNA segment most used is Taq polymerase; and nucleotides the foundation of the DNA molecule.
The method of PCR has three important steps denaturing, annealing, and elongation. The first step is the denaturing of the DNA, denature consist of the disruption of the hydrogen bonds between nitrogenous base pairs, which provide the DNA double strand structure. This denaturing targets the DNA by heating the sample to 94 °- 96 ° C during several minutes, the result is two single DNA strands. The seconds step is the annealing step, the temperature is lowered to 50°- 65° C for several minutes, this allows left and right primers that were added to the mix to base pair to their complementary sequence. The main function of the primers is to enclose the region of DNA that would be amplified; this is possible due to primers allow DNA polymerase to identify where the start of the replication. The third phase is elongation or extension, the temperature once again is raised to 72°- 80° C for a period of several minutes. DNA polymerase synthesizes a new DNA strand using the original DNA strand as the template but this DNA strand will contain the primer in the 5’. The result is two double DNA strands from one double DNA strand. This process continues producing billions of copies of the original DNA segment until all the primers have been used or until the researcher thinks is necessary.
Since the introduction of the PCR technique, it has become a vital technique in research labs due to the production of millions of copies of specific DNA segments in the least amount of time.