How does polymerase chain reaction make genetic testing possible with tiny DNA samples?

Polymerase chain reaction (PCR) makes genetic testing possible with tiny samples by rapidly amplifying a specific segment of DNA into billions of copies. This process allows scientists to obtain the large quantities of genetic material required for analysis from as little as a single molecule of template DNA.12

The technique relies on a cycle of three steps:
* Denaturation: The sample is heated to separate the double-stranded DNA into two single strands.12
* Annealing: Short primers bind to specific, complementary sequences on the template strands.12
* Elongation: A heat-stable enzyme called Taq polymerase adds nucleotides to the primers, synthesizing new complementary strands.12

Because the number of copies doubles with each cycle, repeating this process 25 to 30 times generates sufficient DNA for medical diagnostics, forensic analysis, and genetic testing to detect mutations or pathogens.12