Factors affecting dental DNA in various real post-mortem conditions

摘要

Post-mortem DNA degradation is still the real challenge of DNA-based identification in forensic practise. It is a complicated multifactorial process occurring as a result of the combination of several different environmental effects along with the crucial effect of the elapsed post-mortem interval (PMI). The main purpose of the present study is to evaluate the effect of ante- and post-mortem factors on dental DNA in real forensic cases. Ninety-five teeth extracted from 39 corpses, whose bodies were subject to 6 different post-mortem conditions, were used to evaluate dental DNA amount. In total, 179 DNA extracts isolated from the root of the teeth were examined after removing the crown and sectioning each root into apical and cervical portions. DNA concentration was measured using real-time polymerase chain reaction DNA quantitation kit (PowerQuant (TM) System/Promega). Our results indicate that the post-mortem interval (PMI) is the most important influential factor on dental DNA quantification (p < 0.001). However, in the actual data set, it was confounded with several ante- and post-mortem factors, rendering its actual net effect difficult. The time period of the first 10 days after death yielded the best DNA results from all analysed dental samples. Afterwards, a dramatic decrease in dental DNA was observed in the following time period. Teeth extracted from burnt and fresh corpses yielded the highest amount of DNA, while skeletonized exhumed corpses resulted in the lowest DNA amount. Indeed, dry and indoor conditions demonstrated better results than those in water, outdoors, or buried in the ground. On the other hand, ante-mortem factors including sex, age, tooth type, and tooth root portions did not reveal significant effect on dental DNA yield. We suggest that ante-mortem factors are considerably more subjected to individual variations. Post-mortem factors including PMI, post-mortem conditions, and the relevant surrounding environments have substantial influence on the dental DNA amount yielded.