Tandem Repeats Essay

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Variable number of tandem repeats (VNTR) or mini-satellites were firstly used in forensics to prove unsolved cases. However, where there are usually many mini-satellites of a given type in a genome, there is only one VNTR of each type. They are inherited from parents. Short tandem repeats (STR) is a term that describes any short, repeating DNA sequence. Since different people have different number of repeat units, these regions of DNA can be used to discriminate between individuals. The more STR regions that are tested in an individual, the more discriminating the test becomes.
DNA fingerprint is based on the theory of finger prints which was discovered in India in 1897. A DNA fingerprint signifies characteristic patterns of pieces of
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Hence dna fingerprinting has various applications in forensic science.
METHODS OF DNA FINGERPRINTING
Specific methodologies are implemented in DNA fingerprinting to get a reliable and valid result. The different steps are – isolation, cutting, sorting, analysing of DNA.
ISOLATION OF DNA
Isolation of DNA is mainly done by adding different other digestive enzyme which reacts with constituents in the sample encountered at the crime scene, other than DNA. The different enzymes are proteases which breakdowns amino acids and proteins RNAase which digest RNA particles thus leaving only DNA in the test-tube. Ice cold ethanol is added to this homogenate to precipitate DNA. The DNA can be isolated slowly stirring a glass rod which is known as spooling.
While extraction of dna the sample cells are lysed (broken down) in buffer solution. Other nutrients are digested using specific enzymes except dna. Contaminants ar4e washed off; dna is then recovered in buffer solution or water. Dna amount is quantified by spectrophotometric techniques. Usually, buccal swabs are collected from the suspects as reference sample.
CUTTING OF DNA
RFLP or restriction fragment length polymorphism method is used in which restriction enzyme cuts the DNA at specific sites according to different restriction enzymes. Length of fragments will be different for each individual (everyone’s DNA is unique).
These restriction enzymes are extracted from bacteria.
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