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Blood, hair, saliva, semen and body tissue cells are given as an example of biological eternal which is collected from crime scene. Also, DNA samples have been obtained from vaginal cells transferred to the outside of a condom during sexual intercourse. All individuals in a community have characteristics that allow them to be recognized and distinguished from others, for example, visual characteristics such as height, facial characteristics, skin, eye and hair color and weight. Similarly individuals differ at the cellular and sub-cellular level. Forensic biologists utilize these characteristics.
The methods of biological discrimination can basically be listed as visual coordination, immunological discrimination, discrimination based on protein variations and discrimination based on genetic variations. 1. 1 . The History of Application of DNA Technology to Forensic Science In 1980 Woman and White identified the first hyper variable locus in human DNA. The allelic forms detected at this locus differed in size and were so-called restriction fragment length polymorphisms (Rifle’s). This procedure became the foundation for more exciting discoveries.
Initially, DNA fingerprinting was used to determine family relationships in immigration applications. However, in September 1986 Dry Jeffery was requested by Alice to apply the genetic fingerprinting technology to aid a rape/murder investigation. This highly publicized case, known as the Marlborough Murder Enquiry, was to be the first murder investigation to be resolved by DNA fingerprinting. Shortly after other forms of DNA typing were being reported. PC technology (polymerase chain reaction) was conceived in 1987 and developed by Mulls and co-workers at Sects Corporation.
This kind of analysis determines variation in the length of a defined DNA fragment. The method consists of isolation of DNA from specimen, forensic science By begums fragments according to size by electrophoresis, transfer of restricted DNA onto trolleybuses solid surface, location of region of interest after habitation with labeled ML (Multi-locus probe)/SLP (Single-locus probe) and Addressograph. Usually, the SLP method is preferred over ML because it is more sensitive, easier to interpret and capable of analyzing mixed-DNA samples.
RAFF is an important technique used by forensic scientists in DNA fingerprinting. RAFF analysis measures fragments of DNA containing short sequences that vary from person to person; called Vents (Variable Number Tandem Repeat). VENT is a location in a genome where a short nucleotide sequence is organized as a tandem repeat. These can be found on many chromosomes, and often show variation in length between individuals. Each variant acts as an inherited allele, allowing them to be used for personal or parental identification. Their analysis is useful in genetics and biology research, forensics, and DNA fingerprinting.
After extracting DNA from a sample and amplifying it with the technique known as Polymerase Chain Reaction, a technician adds restriction enzyme that cut the DNA at specific points. The resulting fragments can be sorted by length with gel electrophoresis technology to determine how many times a given VENT is updated. If two different samples show Vents of different lengths, the samples could not have come from the same person. On the other hand, two samples showing Vents of the same length could have come from the same person, or from two people who happen to have Vents of the same length at that location.
By comparing enough Vents from two individuals, however, the likelihood of a coincidental match can be reduced to nearly zero. RAFF testing requires hundreds of steps and weeks to complete, and it has been largely replaced by newer, faster techniques. The RAFF profiling technique is outlined in Figure 1. HOW RAFF works? First of all, double stranded DNA is extracted from blood or semen. The DNA is cut into small pieces by a sequence-specific enzyme for example an enzyme that cuts the DNA wherever a particular sequence of bases occurs. Then the fragments are separated out by a process called electrophoresis.
In electrophoresis process, the sample is put at one end of a bath of a Jelly-like substance called garages gel and a voltage is applied. After that the fragments are charged, and the voltage is applied in such a way as to encourage the fragments to migrate to the other end of the gel. Small fragments move much faster than large ones, so separation on the basis of molecular weight occurs. After electrophoresis the gel and fragments are exposed to HCI to depreciate the DNA and nick the sugar phosphate backbone, as this assists in fragment transfer.