Investigation of the time and temperature stability of 30 InDel locus

Objective: DNA profiling techniques can be used in all cases that require forensic identification or where a direct link between the evidence and the person is investigated. Many different materials (hair/hairs, blood, urine, semen and other biological fluids and their stains) are used for forensic DNA analysis. Crime scene-derived biological samples studied in forensic DNA laboratories are often much less than ideal and negatively affected by environmental conditions. In some cases, the detection of the crime scene can take hours, days or even years. For this reason, biological materials found at the crime scene are exposed to both time and adverse environmental conditions of the crime scene. In this study, it was aimed to genotype 30 InDel loci on biological materials that have passed for a long time, to determine the time and temperature stability of these loci and to compare them with other DNA profiling methods. Materials and Methods: In this study, blood samples taken from healthy volunteers in 1996, dried on gauze and stored in 3 different ambient conditions were used to investigate the effects of temperature and time on the stability of Indel loci. These blood samples were stored at +4°C, room temperature (22-25°C) and +37°C (oven) for 25 years. Among the stored samples, those whose current dated reference samples could be accessed were included in the study. A total of 33 blood stains and current dated blood samples were used as reference. Results: In the quantitation study on the samples; At room temperature, the average DNA amount is 0.168 ng/μl, for +4°C the average DNA amount is 0.205 ng/μl, for reference samples the average DNA amount is 0.938 ng/μl, and for 37 °C, the DNA amount can be detected in all samples studied. was found to be below the level. In our study, when we analyze it on the basis of loci one by one, it is seen that some loci are less stable than others. When we make a comparison between the stability fragment length and those of the same length for more specific evaluation, since it is directly effective, loci with fragments below 140bp could not be detected in only two of the studied samples. One is the HLD99 locus with a fragment length of 108-113 bp, and the other is the HLD128 locus with a fragment length of 113-121 bp. All other unidentified loci have fragment lengths of 140 bp or more. This indicates that the fragmentation in the samples is reduced up to 140bp length. Examining the 140-158 bp long fragmented loci with relatively longer fragments included in the kit, it is seen that HLD 67 lost the most, followed by HLD81 and thirdly by HLD84. Conslusion: It is understood that 30 Indel loci can be successfully analyzed with the Investigator Diplex kit in blood stains that have been kept for more than 25 years, especially if they have not been directly exposed to any artificial heat or sunlight for a long time (especially in samples left in closed areas).