DNA Fingerprinting and STR Analysis
DNA fingerprinting refers to developing a DNA profile based on the analysis of genetic markers in a biological sample. Short tandem repeat (STR) analysis is a technique for evaluating specific regions in DNA.
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DNA
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More than 99.9 percent of your DNA is identical to the DNA of other humans. However, you have inherited regions of DNA, called polymorphisms, that can vary from person to person.
STRs
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One type of DNA polymorphism is short tandem repeats (STRs). STRs are short sequences of DNA that are repeated many times in a head-to-tail manner.
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STR Analysis
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STR analysis looks at the variation in the number of repeats at each STR location. The variation in repeats distinguishes one DNA profile (and person) from another.
Technique
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According to Explore DNA, the first step in STR analysis is to extract DNA from the cells in a sample and amplify the DNA using polymerase chain reaction (PCR). Then, the scientist uses gel electrophoresis, a technique that involves the separation of DNA fragments as they move through a gel matrix, to determine the number of repeats of the STR sequence.
CODIS
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The Federal Bureau of Investigation (FBI) uses a standard set of 13 specific STR regions for CODIS, a database of DNA profiles from convicted offenders, unsolved crimes and missing persons. According to the Human Genome Project, the chances of two individuals having the same 13-region DNA profile is about one in a billion.
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References
Resources
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