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Principles of Forensic DNA for Officers of the Court


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image of an old computer monitor showing mtDNA Sequencing
National Institute of Justice (NIJ) (see reuse policy).

The third step in mtDNA analysis is different:

  • Sequencing: Dideoxy sequencing, a well-established technique that originated in 1977, places fluorescent chemical tags on the terminal nucleotides of DNA fragments that differ in length by a single nucleotide. When these fragments are electrophoresed through a sequence detection instrument, a laser excites each fluorescent tag as it passes by. A camera detects the emitted fluorescence and "reads" the sequence or order of the DNA nucleotides.

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