Abstract: Objective To establish a new method for RNA and DNA co-extraction from the same sample by TRIzol reagent. Methods After the aqueous phase which contained total RNA was removed by traditional TRIzol method, the values of pH of the interphase phase and organic phase were adjusted. The DNA was precipitated with ethanol and purified with DNA IQ^TM system. The purified DNA was measured in quality and quantity. As the template, it was amplified and typed by PCR-STR. The data was compared with that extracted by traditional TRIzol method. Results The DNA extracted by this modified method showed a better result of quality and quantity than that by traditional TRIzol method and a good STR typing. Conclusion The modified TRIzol method is advisable and reliable to simultaneously extract both DNA and RNA from the same sample. It could be used for individual identification and paternity testing to satisfy the need of forensic science.

Key words: forensic genetics, extraction, TRIzol method, blood