The Relationship between Postmortem Interval and DNA Degradation in Different Tissues of Drowned Rats

Abstract

Upon the death of an organism, internal nucleases contained within the cells should cause DNA to degrade into smaller fragments over time, if these fragments can be isolated and visualized, and if the fragmentation is proved to be measurable and quantifiable, it can be a good indicator of the postmortem interval (PMI). This study aimed to evaluate the effect of PMI on DNA degradation in different tissues of drowned rats through quantitative analysis of DNA degradation by easily applicable method. To profile postmortem degradation of DNA, it was extracted, at different PMI (0, 3, 6, 12, 24 hours), from the brain, lungs, spleen, liver and skeletal muscles of drowned rats. Electrophoresis method was used to detect the relationship between the amount of degraded DNA and PMI in different tissues. The present research used a simple, easy, applicable and highly informative electrophoresis method that make it an ideal for the busy forensic laboratory. The postmortem DNA fragmentation observed in this study, reveals a sequential, time-dependent process with the potential for use as a predictor of PMI in cases of drowning. There is linear relationship between the degradation rate of nuclear DNA and PMI in some studied viscera like liver. Some organs like brain showed slower degradation rate of DNA. So, it is considered as a valuable organ for studying DNA in longer PMI. This result shows a potential for use as a future applied method of evaluating time since death.