**1. Introduction**

Polymerase chain reaction (PCR) is one of the most commonly used method in modern molecular biology. The technique was developed by the Nobel laureate, Kary Mullis, in 1984. It is an in vitro process to multiply a target molecule of DNA with extreme precision, making it easy to be handled and examined by routine molecular biological methods [1–4]. Since its inception, PCR has significantly contributed in changing and developing biological sciences. The first PCR machine was introduced in market in 1988. The Human Genome Project has been result of PCR based approaches [5, 6]. Owing to its wide range of applications, numerous variants of PCR techniques have emerged over the past few decades [2–4].

PCR begins with the separation (denaturation) of the strands of a target DNA molecule (known as template) followed by annealing (hybridization) of oligonucleotide primers to the target template. The annealed primers provide a start for the DNA polymerase point to add new nucleotides (deoxynucleoside triphosphates or dNTPs). The sequence of nucleotides to be added is determined by the template. This entire process of the amplification of template, i.e., separation, annealing, and polymerization, is accomplished in vitro by cyclical alterations of temperature [2, 4, 7–10]. DNA polymerases used in PCR originate in thermophilic microorganisms, largely archaea, thriving temperature between 41 and 122°C. This ability to withstand high temperature is requited in PCR to melt or separate the double-stranded DNA. Today, PCR has become a main stay in biotechnology, genomics, diagnostics, systematics, and many more areas [2–6].
