At Sanford Research, Ashley Nettifee, a Research Specialist in the Kareta Lab, uses PCR to study the genes that play a role in the formation of small-cell lung cancer. Scientists, including Nettifee, use the same basic steps to perform PCR experiments. “PCR is a pretty simple process,” says Nettifee, and once you have done a couple experiments, it becomes “muscle memory and it's not as daunting.”

1. All reagents are collected and placed on ice to prevent them from degrading. Reagents, including your DNA sample, primers, and an enzyme called Taq polymerase, are pipetted into small PCR tubes.
2. The PCR tubes are placed in a thermocycler machine programmed to go through cycles of heating and cooling that are necessary to create many copies of the gene of interest.
3. Denaturation: The thermocycler machine heats up, causing the bonds between the two DNA strands to break, creating two single strands of DNA.
4. Annealing: The thermocycler lowers the temperature, allowing small, special segments called primers to recognize and bind to specific DNA sequences.
5. Elongation: Taq polymerase, an enzyme recognizes the primers and initiates the creation of a new complementary DNA strand. This creates two copies of the same DNA segment.
6. The denaturation, annealing, and elongation steps are repeated many times, doubling the number of DNA segments with each cycle. This process can take anywhere from 30 to 120 minutes.
7. After the thermocycler has finished, it is time to analyze the results of the PCR experiment. Many labs use a method called gel electrophoresis to separate the DNA segments in their sample by size.

Nettifee states that there are many benefits to performing PCR experiments. PCR is a “method that you can use to really look at the genome of your samples without having to go through sequencing,” explains Nettifee. Genomic sequencing is a lengthy, expensive process that helps scientists determine the order of nucleotides, the chemical building blocks of DNA, in their sample. Although PCR can not completely replace genomic sequencing, Nettifee says, “it's a good precursor to sort of help speed things along in the lab and be able to isolate whatever part of the genome you want to look at.” After isolating the genes of interest, “based off of size [of your DNA segments], you can kind of gather information about how you want to proceed from there.”

PCR is a useful technique for creating many copies of genes that can be used in different experiments. PCR provides reliable, cost-efficient results, proving it to be a valuable method in both research and clinical laboratories.