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    DNA Profiling using Short Tandem Repeats

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    What is Short Tandum Repeat (STR) and why do we now use that for DNA profiling instead of RFLP? Why is STR more effective and more sensitive?

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    Solution Preview

    In the following I have explained STR and RFLP is details. I have also attached PowerPoint slides for better understanding the concept.

    99.9% of the human DNA sequences are same in every person but there is also a considerable amount of DNA that is different between people. DNA profiling technique exploits this variance to discriminate between different individuals. In the year 1986, Sir Alec Jeffreys of the University of Leicester discovered this technique of DNA profiling.

    Modern DNA profiling uses Short Tandem Repeats (STR) composed of repeated units of 2-8 repeats of nucleotides located in non-coding regions of chromosomes. STR loci (locations on a chromosome) among closely related persons are very similar but unrelated humans have extremely variable STRs. PCR primers are used to target these STR sequences and they are amplified. After amplification the STRs are loaded into an electrophoresis gel and run using opposite voltages. A particular pattern of DNA bands is formed in the gel, which is unique for a particular individual. This DNA banding pattern is like a person's unique fingerprint.

    Advantages of STR analysis:
    1. Each and every STR is polymorphic i.e. a particular type of STR has different sequence repeats (nucleotide repeats) in different individuals.
    2. Different types of STRs can be used to compare between different individuals. For example a DNA ...

    Solution Summary

    DNA profiling is done these days using Short Tandem Repeats (STR) technology which has replaced the previous Restriction fragment length polymorphism (RFLP) technique. The article here describes the advantages of STR technique over RFLP.