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What Is PCR Testing and How Does It Work?

Modern medicine has evolved significantly from the early days. With the integration of new science and medical technology in disease diagnosis, treatment and prognostication, healthcare providers can optimize clinical outcomes. The polymerase chain reaction test represents one of the helpful diagnostic technologies available today.

What Is PCR Testing

Polymerase chain reaction testing refers to a chemical process where billions of copies of a specific DNA or RNA are replicated allowing its amplification and study. Polymerase chain testing has been optimized to enable the diagnosis and study of various disease-causing agents including viruses, and bacteria. PCR testing is also being successfully integrated into forensics and scientific research.  

How Does a PCR Test Work?

PCR tests operate on the principles of genetic material amplification. It typically consists of a series of repeated steps that enable scientists to obtain useful quantities of a genetic sample for study or testing.

Components of a PCR Setup

To conduct polymerase chain testing accurately, the following components must be available:

  • Sample of DNA or RNA to serve as a template for further replication of a genetic sample
  • DNA polymerase test enzymes
  • Primers for DNA/RNA
  • Nucleotides
  • Buffer solutions to optimize replication environment
  • Mutagenic cations (magnesium, manganese, potassium)
  • Reaction tubes to contain process materials
  • Thermal cyclers to optimize reaction temperatures  

Steps in PCR Testing

PCR testing consists of repeated heating and cooling processes called thermal cycles. Once the substrate for the PCR test is introduced into the reaction tubes along with buffers and primers, it is heated in a stepwise manner and then cooled. This heat-cool cycle is repeated about 40 times to complete the amplification process.

Once the DNA amplification is completed, the generated nucleotide materials can be compared with prepared samples from disease-causing organisms or human DNA to detect abnormalities. This comparison allows the detection and diagnosis of various conditions simply by comparing samples to  

Useful Applications for PCR

Polymerase chain reaction testing is currently being used to diagnose a broad spectrum of medical conditions. PCR technology is also being used in forensic medicine and research. Some useful applications of PCR technology are outlined below.

DNA Amplification for Cloning and Sequencing  

The ability of a PCR process to synthesize large volumes of DNA through its amplification process enables it acts as a useful source of genetic material for cloning. PCR can also be used to identify unknown genetic material by subjecting samples to DNA sequencing.

Healthcare: Diagnostic Applications

Polymerase chain testing is currently in use to diagnose numerous health conditions. DNA amplification can allow healthcare providers to search for genetic markers of disease in susceptible individuals.

Prenatal diagnosis of different serious health issues can be made by subjecting samples obtained during amniocentesis, chorionic villus sampling, or cord blood to rapid PCR testing. This can help physicians detect defects in utero and plan early correction.

Cancer detection and therapy can be optimized using polymerase chain testing to check for oncogenes. PCR testing can rapidly analyze and interpret genetic material making diagnosis faster and improving patient outcomes through early institutions of cancer-specific treatment modalities.

Healthcare: Detection and Research for Infectious Diseases

The ability of PCR testing to amplify DNA from various sources allows the detection of disease-causing agents with a high level of accuracy. PCR testing can be used to detect viral, mycobacteria, and bacterial infections.

At present, real-time PCR testing is used to detect the presence of the SARS-CoV-2 viral genome and establish a COVID-19 infection. More established uses of PCRs in infectious diseases include the diagnosis of HIV, tuberculosis, and bacterial infections of the respiratory tract.

Forensic Medicine and Legal Applications

Polymerase chain testing can form the basis for genetic fingerprinting which can be used in distinguishing between persons. Every single person on the planet has a unique genetic makeup that can form the basis for a DNA database.

This is particularly useful in forensic medicine, medicolegal cases, and crime scene investigations. DNA samples retrieved from crime scenes can be amplified using PCR processes and compared to key suspects. This technique is quite accurate and effective in helping decide suspect culpability.

Applications in Research

PCR testing has diverse uses in the field of molecular genetics. Some common uses of PCR technology in research include:

  • Rapid synthesis of DNA pieces
  • DNA sequencing
  • DNA cloning
  • Phylogenic DNA analysis
  • Gene expression studies
  • Mutagenesis

Advantages and Limitations of PCR Testing

PCR testing is a very powerful diagnostic and research tool that produces highly accurate and replicable results. Polymerase chain reactions give clinicians a diagnostic edge allowing them to commence treatment earlier. Rapid diagnosis and treatments have been shown to improve outcomes. However, to produce accurate results, PCR will require exact genetic materials to act as primers and achieve satisfactory amplification. Failure to access necessary genetic will render the entire process unreliable. DNA polymerases used in the amplification process may also undergo denaturation and alter the results. Finally, even minute levels of contamination may be amplified, leading to inaccuracies.