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Principles of Forensic DNA for Officers of the Court

Single Nucleotide Polymorphisms (SNPs)

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Photo of World Trade Center towers collapsing on 9/11
National Institute of Justice (NIJ) (see reuse policy).

The forensic science community continues to seek methods that can expand the range of sample types that may be tested. Just as short tandem repeats (STRs) were developed so that smaller and more degraded samples could be tested than with restriction fragment length polymorphism (RFLP) single nucleotide polymorphisms (SNPs, often pronounced "snips") can be used to obtain results from even smaller and more degraded DNA samples than with STRs.

Conventional DNA testing methods may not yield results when DNA is highly degraded. For example, in the World Trade Center terrorist attack, DNA of the victims was subjected to such extended periods of extreme temperature that conventional testing could not be used to identify human remains.

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