What is PCR used for?

The polymerase chain reaction (PCR) is used to make millions of copies of a target piece of DNA. It is an indispensable tool in modern molecular biology and has transformed scientific research and diagnostic medicine.

PCR and its variations have a wide range of specialised applications and are used by scientists in all fields of biology. The results are also used by scientists in many other fields.

Read What is PCR? for more information about what is involved in the PCR process. Modern biotechnology introduces some of the ways in which DNA technologies have changed what scientists are able to do.

In this interactive, learn about the diverse range of technologies that are possible because of PCR.

Acknowledgements The Science Learning Hub acknowledges the following copyright holders for use of their images within our interactive: Medicine image, Stephen McSweeny, licensed through 123RF Ltd Forensics fingerprint image, Arfo, licensed through 123RF Ltd Food and agriculture sweetcorn image, Maksym Narodenko, licensed through 123RF Ltd Genetics double helix image, Pedro Nogueira, licensed through 123RF Ltd

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Environmental microbiology

PCR contributes to our understanding of many environmental issues, particularly where the detection of microorganisms in the environment is required. PCR allows specific target species to be identified and quantified, even when very low numbers exist. One common example is searching for pathogens or indicator species such as coliforms in water supplies.

Find out how PCR has been used by scientists to explore the environment in Developing an assay, Detecting viruses in the environment, Life in the upper troposphere and Virus hunters

To think about: As a population, we are becoming more aware of the importance of water quality. Whose responsibility should it be to monitor water quality? Who should be allowed access to information about water quality? Whose responsibility should it be to maintain good water quality?

Acknowledgements: Image by Plamen Petrov, licensed through 123RF Ltd.

Consumer genomics

PCR has enabled personalised genome testing. An industry has sprung up offering consumers tailor-made products and services based on information in their genome. For example, nutrigenomics is a specific form of consumer genomics linking genetic information to information about foods that might be better or worse for particular conditions, like inflammatory bowel disease.

Food for thought: How could you be sure the products are really useful? How could you be sure the product claims are scientifically reliable?

Acknowledgements: Image © 2006 Ewan Grant-Mackie.

Forensic science

PCR is very important for the identification of criminals and the collection of organic crime scene evidence such as blood, hair, pollen, semen and soil. DNA fingerprints (also called DNA profiles), identification of familial relationships, genomic DNA isolation and other molecular diagnostics and biochemical analyses can be undertaken forensically through the use of PCR. PCR allows DNA to be identified from tiny samples – a single molecule of DNA can be enough for PCR amplification.

Find out more about DNA extraction, DNA profiling, Forensics – interesting facts, Forensics and DNA or try out the activity DNA detective.

To think about: Currently, forensics experts can only compare crime scene DNA with a databank of DNA samples from known criminals.

What do you think about the idea of creating a national (and international) database of all human DNA profiles to aid in identifying criminals? What could be some implications for our society if everyone’s DNA is recorded and made available to law enforcement? What could be some implications of making the information more widely available?

Acknowledgements: Paul Fleet/ 123RF Ltd

Medicine

PCR has enabled valuable developments in several medical disciplines. For example, it is now used to diagnose and therefore aid in the treatment of many diseases, and it is widely used in research into the diagnosis, treatment and potential cure for a range of many others. Find out more in the article Using PCR in medicine.

Acknowledgements: Image courtesy of Living Cell Technologies Ltd.

Phylogenetics

Minute quantities of DNA, including ancient DNA, from sources such as hair, bones and other tissues can be amplified using PCR. The DNA can then be identified and analysed, and genomes can be sequenced. These processes allow scientists to further their knowledge and understanding of evolution and paleontology. Genome sequencing can also aid in phylogenetic studies, leading to greater understanding of organisms’ evolutionary relationships to each other. This information can be useful to scientists in supporting conservation efforts, studying evolution and understanding unique adaptations.

The Science Learning Hub has several articles highlighting New Zealand examples of research in this area, for example,

Extracting ancient DNA, Wētā poo and DNA, New Zealand Subantarctic Islands coralline algae, Barcoding New Zealand swamp hens, DNA barcoding, DNA sequencing, Sequencing shark DNA and Sequencing the apple genome.

Working for good: How do you think a better understanding of genetics can help with conservation?

Acknowledgements: Image courtesy of Bence Viola, Max Planck Institute.

Food and agriculture

Genetic technologies include a range of techniques that enable the modification of existing organisms for the purpose of improving foods and food production. Of course, selective breeding has been around for centuries, but now the genetic code can be altered deliberately. Genetic manipulation can also be much more targeted and new crops produced much more quickly. In New Zealand, genetic modification is currently controlled by the Hazardous Substances and New Organisms Act administered by the Environmental Protection Authority, although changes in 2017 will see this transferred to the Health and Safety at Work Act and a new set of Hazardous Substances Regulations to be administered by WorkSafe.

Food for thought: What risks could be associated with using genetic technologies to alter our foods? How can we ensure our foods remain safe? What benefits might come from enhanced food production?

Acknowledgements: Image © Goetz Laible, AgResearch, Ruakura.

Using PCR in medicine

What risks could be associated with using genetic technologies to alter our foods? How can we ensure our foods remain safe? What benefits might come from enhanced food production?

Acknowledgements: Goetz Laible, AgResearch, Ruakura.

Genetic research

There are many fields of genetic research that use PCR as an essential tool. The majority of these technologies have multidisciplinary applications. These include the creation, detection and monitoring of genetically modified organisms (GMOs), genetic engineering, gene modification, transgenics, cloning, hybridisation, synthetic biology and directed evolution.

Articles and videos for further information about some of these ideas include Testing for the casein gene, Directed evolution, Genetic modification, Transgenic cows – introduction, Making a transgenic plant, Making a transgenic cow and Bacterial libraries for improving proteins.

Ethics and science: New biotechnologies have raised some public concerns regarding their safety. How could the public make decisions about which techniques and technologies are acceptable and which are not?

Acknowledgements: Richard E. Veilleux, Virginia Polytechnic Institute and State University, Department of Horticulture