Optimization of recovery of human DNA from envelope flaps using DNA IQ™ System for STR genotyping

An optimized protocol based on the DNA IQ™ System has been tested for the extraction of DNA from envelope flaps. DNA is extracted directly without the need for opening and swabbing the flaps. The method is repeatable with <10% R.S.D. (relative standard deviation). The results of a systematic study show that it is an equilibrium extraction, and a small sample volume as well as high lysis buffer content in sample contribute to high extraction efficiency. The extracted DNA requires no further purification steps following its extraction with the DNA IQ™ System. Complete but skewed 15-locus short tandem repeat (STR) profiles, which is typical of degraded of DNA, have been generated from the DNA extracted from 6 to 9 years old casework envelope samples.