Resources and Links
Pixabay Image Source
PCR Strengths and Limitations
https://www.google.com/amp/s/www.medindia.net/amp/patients/patientinfo/polymerase-chain-reaction.htm
PCR Technology Primer
https://www.genome.gov/about-genomics/fact-sheets/Polymerase-Chain-Reaction-Fact-Sheet
We have become familiar with PCR during the COVID-19 pandemic. The COVID-19 diagnostic test was utilized to see who had COVID-19, and what measures needed to be taken to protect the patient. With so much focus on the PCR test, it is important to understand some of the basics of the PCR machine and what its implications are on modern laboratory testing.
What is PCR? Polymerase chain reaction (PCR) is a technology in which small sections of DNA or RNA are replicated from a small sample. PCR testing was created by Kary B. Mullis, who won the Nobel Prize in 1993 for this invention. It is a cornerstone for modern genetic and molecular science, and can be seen in most modern testing laboratories in disease testing locations. In the past, small amounts of DNA/RNA in a sample did not allow for analysis, as a large volume of analyte was required per testing requirements for accuracy. The need for a large volume of sample created problems for lab workers, and the solution for many applications was the creation of the PCR machine.
PCR testing has many uses, and most people first heard about it in relation to COVID-19 testing, AIDS testing and solving crimes with genetic evidence. The key aspect of a PCR machine is its ability to “amplify” the DNA/RNA present by breaking the chain and creating copies. PCR “cycles” are another term we have seen in the news, related to detecting disease in COVID-19 samples. A PCR machine breaks a small sample of DNA/RNA from its double helix shape and a special polymerase chemical duplicates both sides of the helix. Each time the helix is broken and copied is called a “cycle”. The machine heats the liquid chemical mixture including the sample and polymerase chemical, primer, Taq polymerase and others to begin the reaction. The accuracy of reading for the machine is based on the number of cycles used. An optimal number of cycles of determined, which should range between 30-40. With that level of cycles, over a billion copies of the initial sample DNA/RNA will be created, which allows for analysis.
A PCR machine is good for detecting disease, but if too many cycles are used, the result becomes meaningless. PCR machines can also become contaminated, and good infection control standards, quality standards and PPE designed to keep contaminates out of the machine must be used. You must also ensure the proper primers and chemicals are selected before conducting the steps involved to avoid error. Essentially, you cannot test for unknowns with the PCR, and need to have an idea about what you are seeking.
The reduction in volume of sample size, speed of analysis and broad applications make the PCR machine a modern marvel. Such technology has saved lives and has the potential to solve crimes as well. Kary’s Nobel Prize was well deserved.
Posted in Hive and Steemit