Forensic DNA Analysis

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The analysis of genetic markers for identification of biological evidential material in forensic science began with ABO blood group serology in the early part of the 20th century. The appreciation that individual genetic variation could be used to exclude suspected individuals from criminal activity propelled the analysis of other gene products including isozyme and polymorphic protein determination by slab gel electrophoresis. Forensic DNA analysis was introduced in the 1980s and became established with the discovery of polymorphic mini-satellites or variable number of tandem repeat (VNTR) loci which gave rise to the concept of genetic fingerprinting in forensic science (Gill, Jeffreys and Werrett, 1985). This changed emphasis from gene product …show more content…
It is highly sensitive in that it allows DNA typing of very small quantities of DNA from remaining biological sources (Morling, 2009). A limitation of PCR based approaches arises from the susceptibility of the technique encountered when dealing with heterogeneous evidence or aged samples where PCR inhibitors may interact with DNA or could interact with PCR reagents and prevent amplification. Thus sample collection and extraction methods should be optimised to achieve inhibitor-free DNA suitable for forensic analysis (Bessetti, 2007). PCR inhibitors should be removed during DNA extraction process resulting in a product containing high quality DNA that is stable over the long storage times. Extraction strategies cover three main steps; cells lysis to release the DNA molecules, isolation of DNA molecules from other cell components and preparing compatible DNA for PCR amplification (Horsman, Bienvenue, Blasier, and Landers, …show more content…
The corrosive and toxic properties of these solvents especially phenol-chloroform have limited the use of the organic extraction method (Thomas, Moreno, and Tilzer, 1989). Forensic samples are often collect from denim, paper and soli and can be problematic in terms of DNA extraction. Lactoferrin and hematin in blood, indigo dye in denim and cellulose in paper are recognized PCR inhibitors (Norén, Hedell, Ansell & Hedman, 2013). The use of chelating-resin suspension is an alternative method for isolating DNA. Chelex1-100 is composed of both divinylbenzene and iminodiacetate ions; it can bind to transition metal ions like magnesium or act as cheaters for polyvalent metal ions also it able to capture PCR inhibitors found in cellular compounds: it can also prevent DNA degradation (Phillips, McCallum and Welch, 2012). Chelex-100 has a PCR inhibitor role and as a cheating agent may bind to the magnesium ions that are essential cofactors for Taq polymerase, therefore the presence of any resin could have an effect on the amplification efficiency (Hu, Liu, Yi & Huang, 2015). The

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