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Introduction to PCR: Principles and Applications

A comprehensive overview of Polymerase Chain Reaction (PCR) - how it works, variants used in research, and key applications in diagnostics and molecular biology.

What is PCR?

Polymerase Chain Reaction (PCR) is an in vitro technique used to amplify a specific segment of DNA. Developed by Kary Mullis in 1983, it revolutionised molecular biology by making it possible to generate millions of copies of a target sequence from a minimal starting template.

How PCR Works

Denaturation
Annealing
ExtensionTaq polymerase synthesises new DNA strands from the primers.

Common PCR Variants

Variant	Purpose
RT-PCR	Amplify RNA targets via reverse transcription
qPCR	Quantify DNA/RNA in real time
Multiplex PCR	Amplify multiple targets simultaneously
Nested PCR	Improve sensitivity and specificity
Digital PCR	Absolute quantification without a standard curve

Key Applications

Pathogen detection (COVID-19, TB, HIV)
Genetic mutation screening
Forensic DNA profiling
Gene cloning and sequencing prep
Gene-expression studies

Conclusion

PCR remains one of the most versatile tools in molecular biology. Understanding its principles is essential before moving into advanced variants such as qPCR or digital PCR.

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