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FORENSIC BIOLOGY 101
DNA Fingerprinting













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DNA fingerprinting has established itself as an efficient and highly accurate means of determining identities and relationships. It has practically revolutionized the field of forensics, especially concerning rape cases. DNA profiling, as the process is more appropriately called, involves the visualization of special segments of the human genome, which are unique to each individual. These special segments, called Standard Tandem Repeats (STR), can be cut out and separated from the rest of the DNA by two processes: mapping Restriction Fragment Length Polymorphisms (RFLP) and Polymerase Chain Reaction (PCR). After being separated from the other DNA, we can visualize these STR segments and separate them by size using gel electrophoresis. STR sequences can also be directly sequenced using DNA sequencing machines, but this method has yet to move into mainstream usage and is used primarily within the research community. (http://www.usc.edu/dept/engineering/illumin/vol3issue3/dna/index1.html)

DNA is one of the most vital piece of evidence an investigator can collect. It allows a suspect to
 
becomeeither guilty or innocent in a matterof minutes. DNA profiling, as it is more accurately
 
called, is theprocess whereby we visualize a sample of DNA and determine its relationship to other
 
DNA samples. This sounds simple in theory, but how we get from several people's genomes,
 
each of which containsover three billion elements-to a final conclusion is a complex process.
 
D.N.A. (deoxyribonucleic acid) is contained in white blood cells, tissue, bone marrow, hair roots,
 
tooth pulp, semen, saliva and urine.There are currently two popular methods for DNA
 
profiling, which use different elements of the DNA for identification: RFLP
 
(Restriction Fragment Length Polymorphisms) and STR (Short Tandem Repeats). 

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