Polymerase Chain Reaction (PCR)

The Polymerase Chain Reaction (PCR) is a biotechnology technique that allows researchers to quickly create billions of copies of a specific region of DNA in vitro. Today, scientists use this simple and elegant method daily in laboratories across the world for applications from biomedical research to genetic engineering to forensic science and beyond.

Overview

In the early 1980’s, Kary Mullis developed a technique that replicated DNA in vitro using short, synthetic DNA oligonucleotides designed to target a specific sequence (known as primers) and DNA Polymerase I. In a process similar to replication in a cell’s nucleus, the primers would bind to the DNA, directing polymerase to copy the gene sequence. However, after the initial elongation, the sample was heated to denature the newly-formed DNA duplex, then cooled to allow primer binding and extension to happen again. Each time the sample cycled through the different temperatures, the amount of DNA doubled. By repeating this cycle of heating and cooling many times, billions of copies of a specific DNA sequence were produced in a matter of minutes. This simple cycle – anneal, extend, denature – is the basis of the polymerase chain reaction.

Other innovations along the way simplified the process of PCR, allowing it to evolve into the powerful technique we use today. For example, each time the reaction was heated to denature the double-stranded DNA it would deactivate DNA Polymerase I, meaning that the enzyme would need to be added at every cycle of PCR. The discovery of a thermostable DNA polymerase known as Taq revolutionized PCR since it can withstand the extreme changes in temperature required for PCR. A second innovation was the development of a specialized machine that could automatically cycle between temperatures. Using this machine, a single PCR cycle can be completed in less than five minutes without the need to physically move samples between different temperature water baths. Edvotek recognized the power of PCR for the teaching classroom through the development of the NIH SBIR-supported EdvoCycler™.

Edvotek at Home

"Edvotek at Home" is a set of resources to teach the basics of Edvotek’s labs through worksheets and presentations. While we believe in the importance of hands-on learning, these free online learning tools are ideal if you can not perform the hands-on experiments in class. Each set includes a student sheet, an instructor’s guide, and an accompanying powerpoint presentation and results sheet. This resource is provided in a downloadable zipped folder below.

Multiplex PCR Testing of Water Contaminants - Water pollution is a universal problem because clean water is essential for human health, aquatic life, and agriculture. Waterborne microorganisms can cause severe illness, so scientists must monitor the water supply to ensure that it remains safe for human use. In this experiment, students learn how Polymerase Chain Reaction (PCR) is used to detect several waterborne microorganisms simultaneously.

Exploring the Genetics of Taste: SNP Analysis of the PTC Gene Using PCR - Individuals vary greatly in their sensitivity to the bitter compound PTC. Ability to taste the PTC compound is now linked to the presence of a specific taste receptor gene, TAS2R38. The gene has two alleles: the dominant allele (T), which confers the ability to taste PTC, and the recessive non-taster allele (t). A person inherits one copy of the gene from each of his/her parents. The combination of these different alleles within an individual is referred to as a genotype, which in turn dictates phenotype: in this case whether an individual is a “taster” or “non-taster." In this experiment, students will learn how to isolate DNA and use PCR to amplify a segment of the TAS2R38 gene, which is responsible for detecting the bitter taste of PTC. Digestion of the PCR products and analysis by agarose gel electrophoresis are used to differentiate tasters and non-tasters.

Lesson Plans

Modeling DNA Amplification by Polymerase Chain Reaction (PCR) - The objective of this experiment is for students to gain hands-on experience of the principles and practice of Polymerase Chain Reaction (PCR). At the completion of this activity, students should understand the process by which PCR amplifies DNA.

Using EDVO-Kit #335 to Simulate Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) Testing for COVID-19 Infection - The virus responsible for COVID-19 infection, SARS-CoV-2, is a single-stranded RNA virus. This means that the genome of the virus is RNA, not DNA, and therefore the virus cannot be detected by traditional PCR, since PCR requires a DNA template. In order to detect the virus using PCR, Reverse Transcriptase (RT) is used to synthesize complementary DNA (cDNA) copies of the RNA genome. Please note that this is a simulation for educational purposes and should not be used as a substitute for testing using the FDA-validated test by a healthcare professional.

Presentations

These short courses couple theory with active experimentation to help you update your skills and knowledge in various areas of biotechnology.

Transform Your Class Into a Neuroscience Laboratory - Neuroscience is one of the fastest growing fields in science today. Bring it directly into your classroom and make your students neuroscientists for the day! You’ll explore the neurodegenerative disorders Huntington’s and Alzheimer’s. First, we’ll run a genetic analysis on a family who may carry the Huntington gene using PCR and gel electrophoresis. Then, we’ll run an ELISA to explore the biology behind Alzheimer’s disease.

Teaching the Polymerase Chain Reaction (PCR) in One Class Period - How are scientists able to identify genetic mutations and infectious agents? What technique is indispensable to both medical and life science labs? The answer is the Polymerase Chain Reaction (PCR)! Today, we can easily perform PCR in the classroom laboratory. In this hands-on workshop, we will amplify a small region of the Bacteriophage Lambda genome using PCR and analyze it using gel electrophoresis. This quick and easy experiment has been optimized so that the entire experiment can be completed in one 75-minute lab period.

Exploring the Genetics of Taste: SNP Analysis of the PTC Gene Using PCR - Explore the relationship between genotype and phenotype using phenylthiocarbamide (PTC). Some think PTC tastes bitter, while others find it tasteless. The ability to taste PTC has been linked to variations in a taste receptor gene. Learn to use PCR to distinguish between PTC alleles. We will share tips and tricks along the way to ensure experimental success!

Additional Resources

Instructional Videos - For the visual learner:


Troubleshooting Guide - Frequently asked questions, common mistakes, and how to course correct your experiment:
Printable Coloring Pages
Printable Word Puzzles