Polymerase Chain Reaction, PCR, enables researchers to produce millions of
copies of a specific DNA sequence in one to two hours.
This automated process bypasses the need to use bacteria for amplifying DNA.
A PCR reaction starts with a denaturing step.
Samples are heated [from] 94 to 96 degrees celsius for 30 seconds or more
to denature, or separate in two single strands, the target DNA.
Next the temperature is lowered to [between] 50 to 65 degrees celsius for 30 seconds or more.
This allows the left and right primers to anneal to their complementary sequences.
The primers are designed to bracket the DNA region to be amplified.
The temperature is raised to 72 degrees celsius for thirty seconds or more.
This allows the taq polymerase to bind each primed site, and extend or synthesize a new DNA strand.
The temperature is raised to [between] 94 and 96 degrees celsius, denaturing the target DNA as in cycle one.
As before, the temperature cools to [between] 50 and 65 degrees celsius, allowing more primers to anneal.
The temperature is again raised to 72 degrees celsius;
taq polymerase binds to each primed site and synthesizes the new DNA strand.
In subsequent cycles, the process of denaturing, annealing, and extending are
repeated to make additional DNA copies.
After three cycles, the target sequence defined by the primers begins to accumulate.
After thirty cycles, as many as a billion copies of the target sequence are
produced from a single starting molecule.