Những ứng dụng của PCR

PCR có thể được sử dụng cho một loạt rộng rãi các thí nghiệm và phân tích. Một số ví dụ được thảo luận dưới đây
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Những ứng dụng của PCR Những ứng dụng của PCRPCR có thể được sử dụng cho mộtloạt rộng rãi các thí nghiệm vàphân tích. Một số ví dụ được thảoluận dưới đâyVân tay di truyềnGenetic fingerprinting is a forensictechnique used to identify a personby comparing his or her DNA witha given sample, e.g., blood from acrime scene can be geneticallycompared to blood from a suspect.The sample may contain only atiny amount of DNA, obtainedfrom a source such as blood,semen, saliva, hair, etc.Theoretically, just a single strandis needed. First, one breaks theDNA sample into fragments, thenamplifies them using PCR. Theamplified fragments are thenseparated using gelelectrophoresis. The overall layoutof the DNA fragments is calleda DNA fingerprint.Kiểm tra huyết thốngFigure 4: Electrophoresis of PCR-amplified DNA fragments. (1)Father. (2) Child. (3) Mother. Thechild has inherited some, but notall of the fingerprint of each of itsparents, giving it a new, uniquefingerprint.Although these resultingfingerprints are unique (except foridentical twins), geneticrelationships, for example, parent-child or siblings, can bedetermined from two or moregenetic fingerprints, which can beused for paternity tests (Fig. 4). Avariation of this technique can alsobe used to determine evolutionaryrelationships between organisms.[sửa]Chẩn đoán bệnh di truyềnThe detection of hereditarydiseases in a given genome is along and difficult process, whichcan be shortened significantly byusing PCR. Each gene in questioncan easily be amplified throughPCR by using the appropriateprimers and then sequenced todetect mutations.Viral diseases, too, can be detectedusing PCR through amplificationof the viral DNA. This analysis ispossible right after infection,which can be from several days toseveral months before actualsymptoms occur. Such earlydiagnoses give physicians asignificant lead in treatment.[sửa]Tách dòng geneCloning a gene--not to be confusedwith cloning a whole organism--describes the process of isolating agene from one organism and theninserting it into another organism.PCR is often used to amplify thegene, which can then be insertedinto a vector (a vector is a meansof inserting a gene into anorganism) such as aplasmid (acircular DNA molecule) (Fig. 5).The DNA can then be transferredinto a different organism where thegene and its product can be studiedmore closely. Expressing a clonedgene (to express a gene means toproduce the protein that itdetermines the production of) canalso be a way of mass-producinguseful proteins--for example,medicines.Figure 5: Cloning a gene using aplasmid.(1) Chromosomal DNA oforganism A. (2) PCR. (3) Multiplecopies of a single gene fromorganism A. (4) Insertion of thegene into a plasmid. (5) Plasmidwith gene from organism A. (6)Insertion of the plasmid inorganism B. (7) Multiplication orexpression of the gene, originallyfrom organism A, occurring inorganism B.[Gây đột biến điểmMutagenesis is a way of makingchanges to the sequence ofnucleotides in the DNA. There aresituations in which one isinterested in mutated (changed)copies of a given DNA strand, forexample, when trying to assess thefunction of a gene or in in-vitro protein evolution. Mutationscan be introduced into copiedDNA sequences in twofundamentally different ways inthe PCR process. Site-directedmutagenesis allows theexperimenter to introduce amutation at a specific location onthe DNA strand. Usually, thedesired mutation is incorporated inthe primers used for the PCRprogram.Random mutagenesis, onthe other hand, is based on the useof error-prone polymerases in thePCR process. In the case ofrandom mutagenesis, the locationand nature of the mutations cannotbe controlled. One application ofrandom mutagenesis is to analyzestructure-function relationships ofa protein. By randomly altering aDNA sequence, one can comparethe resulting protein with theoriginal and determine thefunction of each part of theprotein.Phân tích mẫu DNA cổUsing PCR, it becomes possible toanalyze DNA that is thousands ofyears old. PCR techniques havebeen successfully used on animals,such as a forty-thousand-year-old mammoth, and also on humanDNA, in applications ranging fromthe analysis ofEgyptian mummies to theidentification of a Russian tsar.Xác định kiểu gene của các độtbiếnThrough the use of allele-specificPCR, one can easily determinewhich allele of a mutation orpolymorphism an individual has.Here, one of the two primers iscommon, and would anneal a shortdistance away from the mutation,while the other anneals right onthe variation. The 3 end of theallele-specific primer is modified,to only anneal if it matches one ofthe alleles. If the mutation ofinterest is a T or C singlenucleotide polymorphism (T/CSNP), one would use tworeactions, one containing a primerending in T, and the other endi ...