Basic Concept of Biotechnology 23

  History of Forensic Genetic Typing More than two decades ago, genetically, polymorphic protein markers were applied to potentially distinguish individuals. But, numerous factors restricted the forensic use of these protein-based genetic systems. The refining power of these markers was low, resultantly, individualization was not difficult. Additionally, the proteins are not available at satisfactory levels for typing in most of the tissues, and they are comparatively more prone to degradation in biological samples in contact with environmental fluctuations. The typing of genetic polymorphisms at the DNA level assists to overcome these restrictions to a much greater extent. Primarily, there is a remarkable amount of dissimilarities at the DNA level to exploit for individuality testing. Second, any biological substance that comprises nucleated cells potentially can be used for DNA polymorphism typing. Third, DNA is found to be more stable in forensic samples. Consequently, with the ...

  Introduction “It has long been an axiom of mine, that the little things are infinitely the most important.” Arthur Conan Doyle It was never been thought that the DNA molecule, a little thing, could prove to be possibly the most important source in the crimeinvestigation. Since the onset of DNA fingerprinting, scrutinization of DNA molecules helps in identifying victims of crimes or accidents andconvicts or exonerates the suspects. It inspires the development of new methods in molecular biology, statistical analysis and usage of databases.DNA evidence speaks more than an eye witness. The word forensic comes from the Latin word forensic which means’ “ of or before the forum ”. The usage of advanced scientific techniques for the implementation of law during criminal and civil cases to get the solution of important questions about the crime is known as forensic science. It includes both science and law. Forensic investigation is the use of the tools of science along with exact scient...

  Restriction Fragment Length Polymorphism (RFLP) Restriction Fragment Length Polymorphism was the first technique established to examine variable lengths of DNA fragments formed through DNA digestion. It uses the variations in DNA sequences due to the different locations of restriction enzyme sites. The method practicesthe use of restriction end nucleases to digest the DNA by cutting it at precise sequence arrangements. The resultant restriction fragments are then separated in gel electrophoresis and then shifted to amembrane using the Southern Blot technique. The separated DNA fragments are transferred and probe hybridisation is used to detect the fragments. In 1980, Wyman and White discovered the first hyper variable locus present in human DNA. The allelic forms identified at this locus fluctuated in size and were so-called restriction fragment length polymorphisms (RFLP's). This procedure became the substance for more exhilarating discoveries. In 1985, Dr Alec Jeffery’s, using ...

  Amplified Fragment Length Polymorphism (AMP-FLP) A range of DNA extraction methods has been used for forensic DNA analysis. For example, digestion of body fluid stains using SDS and proteinase K, followed by purification of DNA by extraction with phenol/chloroform and ethanol precipitation, is very successful and is routinely used for forensic samples analyzed by RFLP typing. However, this method had limitations when applied to a PCR-based DNA typingmethod for forensic analysis viz. HLA DQα typing. For bloodstains, it was observed that, although adequate DNA was obtained for analysis, it could not always amplify using PCR. This failure in amplification process is found to be caused by the existence of hematin in bloodstains, since hematin is an inhibitor of PCR. Another PCR-based DNA typing method, used for the analysis of amplified fragment length polymorphisms (AMP-FLPs) could be implemented in forensic laboratory but it was advantageous to assess a number of DNA extraction met...

  Polymerase Chain Reaction (PCR): During the investigation of a crime, the amount of DNA evidence procured is often very small, thus for efficient DNA profiling, amplification is ideal. PCR allows for the exponential amplification of DNA fragments to the lengths of approximately 10,000bp. PCR is particularly helpful in the amplification of small amounts or degraded samples. In the 1980s, when RFLP was being developed for forensic use, PCR was developed for forensic applications. In 1983, a biochemist, Dr Kary Mullis adopted PCR to amplify DNA fragments of forensic interest in an automated process. He was awarded the Nobel Prize for his discoveryin 1993. PCR solved one of the major struggles facing by forensic biologists. RFLP typing required relatively large quantities of DNA.   The PCR Process PCR methods are very susceptible to contamination by foreign DNA. On this ground, DNA extractions are always performed in a location physically isolated from the desk/lab where the sub...