Extraction of amplifiable DNAis a frequent problem when working with degraded specimens like bone samples. The possibility of obtaining as much information as possible from these samples has a particular significance in many forensic investigations. The present investigation was aimed to assess the efficiency of three organic extraction methods for purifying amplifiable DNA from bone samples. The amount of nucleic acids obtained, the success rate in the amplification of DNA microsatellite (STR) markers and amelogenin by PCR, the influence of PCR inhibitors and environmental conditions, and where the samples were found before their processing in the laboratory, were all evaluated in this investigation for the three methods. Results showed that method A (a modification of FBI method for DNA extraction) performed better in producing not a higher amount but a better quality amplifiable DNA, in comparison with the other two methods evaluated. It was also demonstrated that the quality of the DNA to be amplified by PCR was influenced by the presence of inhibitors and/or contaminants and the environmental conditions where the bone sample was taken from. The worst conditions were observed from aquatic environments. The results suggest that the implementation of some specific modifications in the method A (use of purification columns, reliable quantification methods and different dilutions) would help to obtain better DNA extracts intended to be used in different molecular identification tests.
Keywords: DNA extraction, PCR, STRs, bones, inhibitors, Costa Rica