Polymerase chain reaction

An illustration of the polymerase chain reaction (PCR). Step 1: Solution is heated to 95°C to denature ("unzip") the two strands of the target DNA (A).  Step 2: Solution is cooled to ~55°C to allow the primers to anneal (bind) to the ends of the DNA strands (B). Step 3:  Solution is reheated to ~75°C to allow TAQ polymerase to synthesize complementary copies of each strand. 

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