Chain reaction, especially polymerase chain reaction (PCR), was invented by Kary Mullis in 1983. It has set off a revolution in the field of biology with its unique charm and wide application prospects. Revolutionary change. This technology not only greatly promotes the development of multiple disciplines such as molecular biology, genetics, and medicine, but also provides us with unprecedented convenience and possibility for exploring the mysteries of life, diagnosing diseases, and studying gene functions.

Chain reaction

1. Polymerase chain reaction (PCR) 1. Basic principle: PCR is based on the natural replication process of DNA. Through specific temperature cycles and enzyme catalysis, specific DNA fragments are amplified in large quantities in vitro. In the PCR process, DNA is first heated and denatured into a single strand, then the primer is combined with the complementary sequence of the template DNA single strand, and finally, under the catalysis of DNA polymerase, new DNA is synthesized using deoxyribonucleoside triphosphates (dNTPs) as raw materials. DNA strand. 2. Main steps: Denaturation: Heat the reaction system to high temperature to break the hydrogen bonds between the double strands of the template DNA and dissociate the double strands into single strands. Annealing (renaturation): Reduce the temperature of the reaction system to a lower temperature. At this time, the primer specifically binds to the complementary sequence of the template DNA single strand to form a partial double strand. Extension: Raise the temperature of the reaction system to a suitable temperature, and use dNTPs as raw materials to synthesize a new DNA strand starting from the 3' end of the primer under the catalysis of DNA polymerase. 3. Application fields: Gene cloning and gene expression: A large number of target DNA fragments are obtained through PCR amplification, and then experiments such as gene cloning and gene expression can be carried out. Gene sequencing and mutation analysis: After PCR amplification of the target DNA fragment and sequence determination, a large amount of sequence information can be obtained, which provides strong support for studying the structure, function and mutation type of genes. Pathogen detection and identification: By designing primers for pathogen-specific DNA sequences for PCR amplification, the presence of pathogens can be quickly and accurately detected and used for pathogen identification and typing. Diagnosis of genetic diseases: By designing primers for genes related to genetic diseases for PCR amplification, it is possible to detect whether patients have mutated genes, which is helpful for early diagnosis of genetic diseases, gene therapy and family genetic counseling. Forensic applications: By designing primers for individual-specific DNA sequences for PCR amplification, rapid identification of DNA samples from crime scenes can be achieved. Environmental monitoring and evolutionary research: PCR technology can help scientists assess and monitor biodiversity in ecosystems and detect microorganisms in environmental samples.

2. Other applications of chain reaction in biology Although PCR is the most typical application of chain reaction in biology, the concept of chain reaction can also be extended to other biological processes. For example, chain reaction-like processes may also exist in signaling, metabolic pathways, and gene regulatory networks. These processes typically involve a series of interconnected biochemical reactions, in which the product of one reaction triggers the next reaction to occur, thus forming a continuous, self-sustaining chain of reactions.

Chain reaction has important application value in biology, especially DNA amplification achieved by PCR technology. This technology has become an indispensable tool in the fields of modern biology and medicine, providing powerful support for genetic research, disease diagnosis and treatment. At the same time, the concept of chain reaction can also be extended to other biological processes, providing new perspectives and methods for in-depth understanding of the complexity and functions of organisms.

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