Lec -14: Polymerase Chain Reachtion (PCR) | By Dr. Rajesh Tokriya

This lecture by Dr. Rajesh Tokriya provides a comprehensive introduction to the Polymerase Chain Reaction (PCR) for Class 12 Biology students, particularly those preparing for NEET and other competitive exams. The instructor begins by explaining the concept of PCR using an analogy to a photocopy machine, emphasizing that PCR amplifies a specific DNA segment (gene of interest) into millions of copies in a short time. He then breaks down the term ‘Polymerase Chain Reaction’ into its components: polymerase (the enzyme synthesizing new DNA), chain (repetition of events), and reaction (controlled conditions). The lecture covers the definition of PCR as an in vitro technique for selective amplification of a specific DNA segment, contrasting it with in vivo processes. The history of PCR is discussed, crediting Kary Mullis for its discovery in 1983, for which he received the Nobel Prize. The essential components required for PCR are detailed: template DNA (containing the gene of interest), two primers (short oligonucleotides providing a free 3’-OH group), deoxyribonucleotide triphosphates (dNTPs), and a heat-stable DNA polymerase, specifically Taq polymerase isolated from Thermus aquaticus, and Pfu polymerase from Pyrococcus furiosus. The lecture sets the stage for explaining the PCR process, which involves repeated cycles of denaturation, annealing, and extension.