What is polymerase chain reaction? Polymerase chain reaction, commonly known as PCR, first emerged in the 1980s when Mullis invented a simplified DNA amplification method. This invention marked a breakthrough in the field of molecular biology, signifying the true birth of PCR technology.The core principle of PCR is based on the semi-conservative replication of DNA, where double-stranded DNA is unwound and undergoes semi-conservative replication to produce amplified products. This allows for the exponential amplification of trace amounts of target DNA fragments in vitro. PCR technology is not only highly sensitive, rapid, and simple to perform but also offers excellent reproducibility and high yield, making it widely applicable.

During the entire reaction, the technique requires setting different denaturation, annealing, and extension temperatures and durations based on the length and GC content of the target DNA fragment, all under enzymatic conditions. Before starting the experiment, it is necessary to prepare template DNA, specific primers, DNA polymerase, dNTPs, and a buffer containing Mg²⁺. The template DNA can be derived from tissues or cells of any species. Typically, during template DNA preparation, it undergoes extraction and purification using chloroform and phenol reagents, followed by ethanol precipitation to obtain a pure template. The template in the PCR reaction system must be free of impurities. If RNA is used as an example, pure RNA must first be obtained and then reverse-transcribed into cDNA to serve as the template in the PCR reaction system.

Polymerase Chain Reaction (PCR) is a widely used technique in molecular biology and biochemical research for amplifying DNA fragments. Below are the general steps for performing a PCR experiment:

1. Sample Preparation: Prepare the DNA template to be amplified, such as genomic DNA, cDNA, or other DNA samples.

2. Reaction Mixture Preparation: Prepare the PCR reaction mixture, which typically includes the DNA template, primers, dNTPs (deoxynucleotide triphosphates), Taq polymerase (or another DNA polymerase), buffer, and water.

3. Thermal Cycling Program Setup: Set up the PCR thermal cycling program, which usually includes an initial denaturation step, followed by cycles of denaturation, annealing, and extension, and a final extension step.

4. PCR Amplification: Place the PCR reaction mixture in a thermal cycler and run the amplification according to the programmed protocol.

5. PCR Product Analysis: Analyze the PCR products using techniques such as gel electrophoresis, real-time quantitative PCR (qPCR), or other methods to verify the amplified DNA fragments.

6. Result Interpretation: Evaluate the PCR results to determine whether the target DNA fragment was successfully amplified.

7. Applications: Depending on the experimental purpose, the PCR products can be used for various applications, including DNA sequencing, cloning, gene expression analysis, genotyping, and more.

Note: When conducting PCR experiments, it is crucial to follow laboratory safety protocols and standard operating procedures to ensure both accuracy and safety. Additionally, specific PCR conditions (including temperature, primer design, and reaction duration) should be optimized according to the target amplification sequence and the characteristics of the DNA template.

Specific primers are a pair of primers designed based on the sequence of our target gene, namely the 3' and 5' primers. The length of each primer is typically between 18–26 bp, with a GC content of 40–60% being optimal. Internal secondary structures should be avoided within the forward and reverse primers to prevent primer complementarity.In the PCR reaction system, different DNA polymerases can be selected based on the requirements of downstream experiments. For instance, if high fidelity is needed for subsequent experiments, a high-fidelity enzyme should be chosen. The Mg²⁺ in the buffer can influence the specificity of the reaction and the yield of the amplified fragment, so an appropriate buffer must be selected.Finally, the reaction temperature and cycle number should be set. The denaturation temperature typically ranges between 90–96°C and lasts for about 30 seconds. The annealing temperature is usually set 5°C below the primer's Tm value, generally between 45–55°C. The extension temperature depends on the sequence of the target gene, while the extension time is determined by the enzyme's synthesis speed and the length of the fragment.Formula: Tm = 4(G + C) + 2(A + T)

KMD Bioscience provides PCR template extraction services to ensure optimal PCR products, laying a solid foundation for subsequent experiments. With extensive experience in molecular experiments, KMD Bioscience is capable of handling sample preparation and PCR services for any type of specimen, delivering higher-quality services to our clients.