Chloroplast gene markers detect diatom DNA in a drowned mice establishing drowning as a cause of death.

Diatoms are unicellular microalgae with cell wall made up of rigid silica found in all open water bodies. They thus resist degradation and hence are important tool to diagnose cause of death in drowned bodies. The nitric acid digestion method practiced conventionally in forensic science laboratories has limitations due to manual error. Plant chloroplast genes found in diatoms such as ribulose-1,5-bisphosphate carboxylase oxygenase (rbcL-3P) and rbcL, universal plastidic amplicon (UPA), and photosynthesis I P700 apoprotein chlorophyll Al (psaA), which play an important role in photosystems I and II of photosynthesis, are tested to diagnose drowning in experimental mice. It was seen that psaA-2 showed amplification at 150 bp in all biological samples. The sequences of psaA-2 gene marker showed 100% proximity to Thalassiosira weissflogii and rbcL-3P showed 99% resemblance to Pseudo-nitzschia multiseries. On the other hand, in postmortem drowned biological samples, the chloroplast-based gene marker failed to show any amplification.