Gene Technology: PCR and Gel Electrophoresis

This lesson covers two fundamental techniques in molecular biology — the polymerase chain reaction (PCR) and gel electrophoresis — as required by the Edexcel A-Level Biology specification (9BI0, Topic 7).

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The Polymerase Chain Reaction (PCR)

PCR is a technique used to amplify (make millions of copies of) a specific segment of DNA in vitro (outside a living organism). It was developed by Kary Mullis in 1983 and has revolutionised molecular biology, forensics and medicine.

Why Is PCR Needed?

Many applications require large quantities of a specific DNA fragment, but the starting sample may contain only tiny amounts of DNA (e.g. a single hair follicle at a crime scene, ancient DNA from fossils, or a small tissue biopsy). PCR can amplify a target sequence from as little as a single molecule of DNA.

Requirements for PCR