PCR should stand for "Pretty Cool Reaction"

Amanda Price

PCR actually stands for polymerase chain reaction, this reaction is used to amplify DNA segments. The technique denatures and renatures the short segments of DNA using DNA polymerase 1(1).

Figure 1. Illustration of the PCR process in which the DNA segment is copied into millions of identical DNA segments.

The first step of PCR is denaturation which occurs by heating the DNA to a temperature of roughly 96 degrees Celsius. This allows the DNA to be separated and provides a single-stranded template. The second step of the reaction is cooled down to about 60 degrees Celsius which allows for the primers to bind the complementary sequences. The final step of the reaction is raising the temperature so that taq polymerase extends the primers and creates a new strand of DNA. This process is repeated 25-35 times in a typical reaction and creates millions of copies in a relatively short period of just 2-4 hours (2).

PCR is used in a variety of ways in the field of biology. It has been used to detect genetic diseases, ancestral and evolutionary studies, prenatal testing, and even the detection of infectious diseases(3).

Since PCR can amplify the DNA into millions of copies it can take a singular molecule of DNA and turn it into thousands of copies. This has been groundbreaking in the field of forensics. The DNA found at a crime scene can be amplified into a readable sample and help in making correct convictions of criminal cases (4). The addition and expansion of PCR technology have allowed forensic DNA analysis to become more rapid and more sensitive (5).

While the advancements of PCR today have skyrocketed our ability to preserve DNA in the modern day, PCR continues to have even more promise in the future. PCR is expected to play a massive role in future molecular diagnostic techniques. It is expected that both RT-PCR and qPCR (two separate methods of the polymerase chain reaction) will be essential in immunomagnetic exosomal RNA and mRNA purification respectively (6).

PCR infographic: https://www.canva.com/design/DAF9_l_2GcI/ZabisoYsTHtSwn_NFmGzIA/edit?utm_content=DAF9_l_2GcI&utm_campaign=designshare&utm_medium=link2&utm_source=sharebutton

References

1 - Khehra N, Padda IS, Swift CJ. Polymerase Chain Reaction (PCR) [Updated 2023 Mar 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK589663/

2 - Khan Academy. (n.d.). Polymerase chain reaction (PCR) (article). Khan Academy. https://www.khanacademy.org/science/ap-biology/gene-expression-and-regulation/biotechnology/a/polymerase-chain-reaction-pcr

3 - Miley, M. (2024, March 2). 17 astonishing facts about polymerase chain reaction (PCR). Facts.net. https://facts.net/science/chemistry/17-astonishing-facts-about-polymerase-chain-reaction-pcr/

4 - DNA testing procedures. Bureau of Criminal Apprehension. (n.d.). https://dps.mn.gov/divisions/bca/bca-divisions/forensic-science/Pages/dna-procedures.aspx#:~:text=PCR%20is%20a%20process%20in,in%20both%20quantity%20and%20quality.

5 - Crime scene and DNA basics for forensic analysts: Polymerase chain reaction (PCR). National Institute of Justice. (n.d.). https://nij.ojp.gov/nij-hosted-online-training-courses/crime-scene-and-dna-basics-forensic-analysts/history-and-types-forensic-dna-testing/polymerase-chain-reaction-pcr#:~:text=In%201983%2C%20Kary%20Mullis%20developed,became%20more%20rapid%20and%20sensitive.

6 - Zhu, H., Zhang, H., Xu, Y., Laššáková, S., Korabečná, M., & Neužil, P. (2020). PCR past, present, and future. BioTechniques, 69(4), 317–325. https://doi.org/10.2144/btn-2020-0057

image - Polymerase chain reaction (PCR). Genome.gov. (n.d.). https://www.genome.gov/genetics-glossary/Polymerase-Chain-Reaction