STR analysis in bones exposed to Brazilian tropical climate

Abstract Brazil has one of the highest homicides rates in the world. In this context, many cases of post mortem human bones that have been exposed to adverse environmental conditions and contaminants are the only materials available for analysis. Humid tropical climate with high rainfall and temperature has a direct influence on bone material that has been exposed to those conditions resulting in cell loss and DNA degradation. This study aimed to extract DNA using a commercial kit and organic extraction to evaluate their success in amplifying 15 STR markers from human skeletal remains exposed to tropical conditions. Compact bone fragments were used from the femoral diaphysis of 20 skeletonized corpses, found in the period 1998–2007 in Ribeirao Preto, Sao Paulo, Brazil. Fragments were sanded and pulverized and DNA was extracted from 150mg of bone powder using commercial kit and phenol chloroform with alcohol precipitation. Samples were quantified with Duo DNA Quantifiler kit (Applied Biosystems) and amplified by PowerPlex ® 16 HS System (Promega). DNA could be quantified in 60% of samples by employing the commercial kit extraction. Nevertheless, a complete profile was not obtained in any case, using organic or commercial extraction methods. Partial profiles were obtained in 60% of cases and markers with up to 264 base pairs were amplified. Our results show that is possible to obtain short amplicons, demonstrating DNA degradation and that there is a need of mini STR analysis in these types of sample.