Những ứng dụng của PCR

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Số trang Những ứng dụng của PCR 14 Cỡ tệp Những ứng dụng của PCR 1 MB Lượt tải Những ứng dụng của PCR 0 Lượt đọc Những ứng dụng của PCR 1
Đánh giá Những ứng dụng của PCR
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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 Vân tay di truyền Genetic fingerprinting is a forensic technique used to identify a person by comparing his or her DNA with a given sample, e.g., blood from a crime scene can be genetically compared to blood from a suspect. The sample may contain only a tiny amount of DNA, obtained from a source such as blood, semen, saliva, hair, etc. Theoretically, just a single strand is needed. First, one breaks the DNA sample into fragments, then amplifies them using PCR. The amplified fragments are then separated using gel electrophoresis. The overall layout of the DNA fragments is called a DNA fingerprint. Kiểm tra huyết thống Figure 4: Electrophoresis of PCRamplified DNA fragments. (1) Father. (2) Child. (3) Mother. The child has inherited some, but not all of the fingerprint of each of its parents, giving it a new, unique fingerprint. Although these resulting 'fingerprints' are unique (except for identical twins), genetic relationships, for example, parent- child or siblings, can be determined from two or more genetic fingerprints, which can be used for paternity tests (Fig. 4). A variation of this technique can also be used to determine evolutionary relationships between organisms. [sửa]Chẩn đoán bệnh di truyền The detection of hereditary diseases in a given genome is a long and difficult process, which can be shortened significantly by using PCR. Each gene in question can easily be amplified through PCR by using the appropriate primers and then sequenced to detect mutations. Viral diseases, too, can be detected using PCR through amplification of the viral DNA. This analysis is possible right after infection, which can be from several days to several months before actual symptoms occur. Such early diagnoses give physicians a significant lead in treatment. [sửa]Tách dòng gene Cloning a gene--not to be confused with cloning a whole organism-describes the process of isolating a gene from one organism and then inserting it into another organism. PCR is often used to amplify the gene, which can then be inserted into a vector (a vector is a means of inserting a gene into an organism) such as aplasmid (a circular DNA molecule) (Fig. 5). The DNA can then be transferred into a different organism where the gene and its product can be studied more closely. Expressing a cloned gene (to express a gene means to produce the protein that it determines the production of) can also be a way of mass-producing useful proteins--for example, medicines. Figure 5: Cloning a gene using a plasmid. (1) Chromosomal DNA of organism A. (2) PCR. (3) Multiple copies of a single gene from organism A. (4) Insertion of the gene into a plasmid. (5) Plasmid with gene from organism A. (6) Insertion of the plasmid in organism B. (7) Multiplication or expression of the gene, originally from organism A, occurring in organism B. [Gây đột biến điểm Mutagenesis is a way of making changes to the sequence of nucleotides in the DNA. There are situations in which one is interested in mutated (changed) copies of a given DNA strand, for example, when trying to assess the function of a gene or in invitro protein evolution. Mutations can be introduced into copied DNA sequences in two fundamentally different ways in the PCR process. Site-directed mutagenesis allows the experimenter to introduce a mutation at a specific location on the DNA strand. Usually, the desired mutation is incorporated in the primers used for the PCR program.Random mutagenesis, on the other hand, is based on the use of error-prone polymerases in the PCR process. In the case of random mutagenesis, the location and nature of the mutations cannot be controlled. One application of random mutagenesis is to analyze structure-function relationships of a protein. By randomly altering a DNA sequence, one can compare the resulting protein with the original and determine the function of each part of the protein. Phân tích mẫu DNA cổ Using PCR, it becomes possible to analyze DNA that is thousands of years old. PCR techniques have been successfully used on animals, such as a forty-thousand-year- old mammoth, and also on human DNA, in applications ranging from the analysis of Egyptian mummies to the identification of a Russian tsar. Xác định kiểu gene của các đột biến Through the use of allele-specific PCR, one can easily determine which allele of a mutation or polymorphism an individual has. Here, one of the two primers is common, and would anneal a short distance away from the mutation, while the other anneals right on the variation. The 3' end of the allele-specific primer is modified, to only anneal if it matches one of
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