Polymerase Chain Reaction
Polymerase Chain Reaction - Related Videos
13:27
PCR: The Polymerase Chain Reaction
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2023
The polymerase chain reaction, or PCR, is a technique used to amplify DNA through thermocycling – cyles of temperature changes at fixed time intervals. Using a thermostable DNA polymerase, PCR can create numerous copies of DNA from DNA building blocks called dNTPs. There are three steps in PCR: denaturation, annealing, and elongation. Denaturation is the first step in the cycle and causes the DNA to melt by disrupting hydrogen bonds between the bases resulting in single-stranded DNA. Annealing...
03:25
Quantitative Polymerase Chain Reaction to Enumerate Bacteriophages
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2025
In this video, we discuss the quantitative polymerase chain reaction, qPCR, to enumerate T7 bacteriophages through DNA quantification. The fluorescent dye in the PCR mixture binds with the newly synthesized DNA strands and emits fluorescence, which is measured.
09:00
Polymerase Chain Reaction: Basic Protocol Plus Troubleshooting and Optimization Strategies
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Cited by 492 •
2012
PCR has emerged as a common technique in many molecular biology laboratories. Provided here is a quick guide to several conventional PCR protocols. Because each reaction is a unique experiment, optimal conditions required to generate a product vary. Understanding the variables in a reaction will greatly enhance troubleshooting efficiency, thereby increasing the chance to obtain the desired result.
13:34
Detecting Environmental Microorganisms with the Polymerase Chain Reaction and Gel Electrophoresis
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2023
Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - Arizona University Demonstrating Author: Bradley Schmitz Polymerase chain reaction (PCR) is a technique used to detect microorganisms that are present in soil, water, and atmospheric environments. By amplifying specific sections of DNA, PCR can facilitate the detection and identification of target microorganisms down to the species, strain, and serovar/pathovar level. The technique can also be utilized to characterize entire...
02:30
Gradient Polymerase Chain Reaction to Determine the Optimum Annealing Temperature
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2025
This video demonstrates the gradient polymerase chain reaction for optimization of the annealing temperature of primers, which sets gradient annealing temperature along wells. The effect of different annealing temperatures is determined by the yield of amplified products that helps to optimize the reaction condition.
FAQs
The three stages perform different jobs in sequence. Denaturation separates the DNA strands, primer annealing directs the reaction toward the selected sequence, and extension allows the thermostable DNA polymerase to build copies. Repeating this sequence increases the amount of the targeted genetic material, turning a difficult-to-detect signal into material that can be analyzed.
Primers provide the sequence-specific starting points for DNA synthesis, so their placement determines which region becomes the target. This selectivity allows PCR to focus on a particular gene or other DNA segment rather than copying all available genetic material. In practice, primer-directed targeting supports gene identification, mutation analysis, and pathogen detection.
The polymerase extends the annealed primers by producing new DNA copies, but it must remain functional through the repeated denaturation stages. A thermostable DNA polymerase supplies that stability, allowing the reaction to proceed through successive cycles without losing the enzyme responsible for extension. Its activity is therefore central to accumulating detectable target DNA.
Small starting samples may contain too little target DNA for direct detection or detailed analysis. PCR repeatedly copies the selected sequence, generating millions of target copies from limited genetic material. This amplification improves sensitivity and produces measurable quantities, enabling investigators to examine trace samples in applications such as forensic testing and infection studies.
A PCR workflow begins with DNA containing the sequence of interest, followed by repeated cycles of denaturation, primer annealing, and extension. During denaturation, strands separate; annealing positions the primers; and extension uses thermostable DNA polymerase to copy the target. The completed reaction yields amplified DNA that can be detected and analyzed.
PCR is useful when investigators need to identify, detect, or analyze a specific DNA sequence, especially when only a small amount of genetic material is available. Biology applications include gene identification, cloning, mutation analysis, pathogen detection, and forensic testing. The method can also support studies of genetic variation and biological relationships.
For pathogen detection, selective amplification can make DNA associated with an infectious organism easier to detect. In genetic studies, targeting particular sequences helps researchers examine variation or identify mutations. Because PCR converts limited genetic material into measurable quantities, it connects sequence-specific testing with biological questions about infection, heredity, and differences among samples.