Basics of PCR

Let’s now review the basic components of a PCR reaction. It starts with a strand of double-stranded template DNA that includes the target sequence. Also needed are primers—short, single-stranded DNA sequences that are complementary to a specific part of the target sequence. dNTPs, or the building blocks for new DNA strands, are included, as well as the DNA polymerase, the enzyme that uses single- stranded DNA as a template to synthesize a complementary DNA strand. The reaction runs in a buffer containing magnesium ions, which are crucial for the activity of the enzyme. While early PCR was performed by physically moving tubes from one water bath to another to incubate the reaction at the specific temperatures for each step of the process, today PCR is performed in a thermal cycler instrument, which automates the cycling of the reaction steps through the different temperatures. Thanks for watching!