Forensics, polymerase chain reaction

The use of agarose as an electrophoretic method is widespread (32—35). An example of its use is in the evaluation and typing of DNA both in forensics (see Forensic chemistry) and to study heritable diseases (36). Agarose electrophoresis is combined with other analytical tools such as Southern blotting, polymerase chain reaction, and fluorescence. The advantages of agarose electrophoresis are that it requires no additives or cross-linkers for polymerization, it is not hazardous, low concentration gels are relatively sturdy, it is inexpensive, and it can be combined with many other analytical methods. 

While many diseases have long been known to result from alterations in an individual s DNA, tools for the detection of genetic mutations have only recently become widely available. These techniques rely upon the catalytic efficiency and specificity of enzyme catalysts. For example, the polymerase chain reaction (PCR) relies upon the ability of enzymes to serve as catalytic amplifiers to analyze the DNA present in biologic and forensic samples. In the PCR technique, a thermostable DNA polymerase, directed by appropriate oligonucleotide primers, produces thousands of copies of a sample of DNA that was present initially at levels too low for direct detection. 

Kasai K, Nakamura Y and White R 1990) Amplification of a variable number of tandem repeats (VNTR) locus (pMCTii8) by the polymerase chain reaction (PCR) and its application to forensic science. ] For Sci 35 1196-1200. 

Provided a sample of DNA can be obtained, a restriction analysis can be carried ont. A match between the restriction fragments from a sample of DNA left at the scene of a crime and that of a snspect is a valnable tool in forensic science. The usefulness of this techniqne is increased enormously by combining it with the polymerase chain reaction, since the amount of DNA extracted from a very small amount of tissue can be increased enormonsly, providing enough for a restriction analysis. Tissne samples as small as a single cell, a hair, a drop of sahva, a piece of dandruff or a smear of semen are snfflcient to prodnce enough DNA. It has produced a revolution in forensic science. However, caution must be applied to interpretation of the results for... 

The polymerase chain reaction (PCR), developed by Mullis, is a simple and most effective way of amplifying, i.e. producing multiple copies of, a DNA sequence. It finds applications in all sorts of areas not immediately associated with nucleic acid biochemistry, e.g. genetic screening, medical diagnostics, forensic science, and evolutionary biology. The general public is now well aware of the importance... 

More recently, the forensic application of DNA testing has dramatically enhanced the ability to determine the source of a blood sample. Two procedures are in forensic use restriction fragment length polymorphism (RFLP) and polymerase chain reaction (PCR). 

Forensic Science Introduction DNA Extraction Methods in Forensic Analysis Polymerase Chain Reaction in the Forensic Analysis of DNA... 

Since polymerase chain reaction can be used to amplify a specific DNA fragment in the presence of countless other sequences, it has proven to be a powerful tool in a number of different fields of study. One area that has benefited tremendously from this technique is the field of forensic science. Any biological sample recovered from a crime scene that contains DNA (a single hair, a drop of blood, skin cell, saliva, etc.) can be subjected to PCR. Primers complementary to repetitive DNA sequences found throughout the human genome are... 

Key papers were reviewed to provide the reader with a road map to the literature that covers this area. The chapter concluded with a brief discussion of the role of the polymerase chain reaction in forensics. 

Polymerase chain reaction(PCR) Technique for amplification of small amounts of DNA. starting with a few molecules and yielding sufficient material to analyze the sequence. Also widely used in forensic DNA analysis. 

D. Polymerase chain reaction (PCR) is an in vitro technique used for rapidly producing large amounts of DNA. It is suitable for clinical or forensic... 

Diagnostic RFLP methods employ DNA that is readily available from the white cells of patient blood samples. Forensic methods, on the other hand, use DNA samples of unpredictable (usually low) quantity furthermore, if the DNA sample is old and has been exposed to sunlight (UV radiation), the DNA may be present as cleaved fragments rather than intact genes. In such cases, the available DNA is amplified in concentration using the polymerase chain reaction (PCR).10 PCR technology has revolutionized DNA analysis, and has made such general forensic tests feasible. 

In forensic cases, DNA samples can be extracted and purified from small specimens of skin, blood, semen, or hair roots collected at the crime scene. DNA that is suitable for analysis even can be obtained from dried stains of semen and blood. The RFLP analysis performed on these samples then is compared to those performed on samples obtained from the suspect. If the RFLP patterns match, it is then beyond reasonable doubt that the suspect was at the crime scene. In practice, several different probes containing different types of repetitious sequences are used in the hybridizations in order to satisfy certain statistical criteria for absolute, positive identification. The use of different restriction enzymes allow for accuracies in positive identifications of greater than one in 100 million. In recent years, polymerase chain reaction (PCR), a method that amplifies DNA, has made it possible for very small amounts of DNA found at crime scenes to be amplified for DNA fingerprinting analysis. Using specific probes to prime DNA polymerase, many copies of the targeted areas of DNA can be synthesized in vitro and subsequently analyzed. 

Using a heat-stable DNA polymerase produced by the bacterium Thermus aquaticus and specific DNA primers, polymerase chain reaction allows the amplification of DNA sequences that are present in small quantities. This technique is useful in genetic screening, diagnosis of viral or bacterial disease, and forensic science. 

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