A method for extracting DNA from hard tissues for use in forensic identification.

Abstract

With deceased and decayed bodies, personal identification is performed using hard tissue DNA, commonly extracted from bone. The quantity and quality of DNA used in the polymerase chain reaction (PCR) amplification step is critical for a successful outcome. Since enamel is the strongest tissue in the human body, it was hypothesized that teeth may preserve DNA better than bones. In the present study, porcine teeth and bone samples were exposed to a variety of environments that imitated personal identification conditions, and DNA extracted from the teeth and bone samples was compared, using a PCR amplification method. The porcine teeth and bones were exposed to 11 different conditions for 5 different time periods to imitate a series of common crime scenes. DNA was extracted by a standard phenol-chloroform method. To test DNA quality, PCR was performed with primers designed to amplify porcine β-actin (ACTB) and mitochondrial DNA (mtDNA) sequences. The results demonstrated that the quality of DNA extracted from teeth was greater than that extracted from bone in the following environments: Buried in sand, soaked in caustic soda and burnt with rubber. By contrast, the quality of DNA extracted from bone was greater than that extracted from teeth when samples were buried in soil or submerged in water. There was no discernable difference in the quality of DNA extracted from bones and teeth in several environments, including being submerged in seawater, soaked in sulfuric acid, left in open air, and stored at 4, -20 and -80°C. Additionally, the results suggested that PCR using mtDNA primers performed better than that using ACTB primers. Finally, it was indicated that components of seawater may inhibit PCR amplification. The preliminary data reported here may provide basic guidelines for selecting the optimum source of DNA in each case.