Effect of ultraviolet C radiation on biological samples.

AIM: To examine the influence of ultraviolet C (UVC) radiation on blood, saliva, semen, and naked DNA samples for preventing DNA cross-contamination on working surfaces in laboratories. METHODS: Blood, saliva, semen, and DNA isolated from buccal swab samples were obtained from a single male donor and applied to the laboratory working surfaces. UVC radiation was applied to these diluted and undiluted samples with or without previous decontamination of the working surfaces with 10% sodium hypochlorite and 20% ethanol. Genomic DNA was extracted using Chelex. After quantification, DNA was amplified using the AmpFlSTR® NGM™ PCR Amplification Kit. We tested and statistically analyzed DNA concentration, UVC dose, sample volume, radiation time, the number of correctly detected alleles on genetic loci, and the number of correctly detected alleles in four groups in which 16 loci were divided. RESULTS: When working surfaces were not decontaminated and were treated only with UVC radiation in the laboratory, the genetic profile for naked DNA could not be obtained after 2 minutes of UVC radiation and for saliva after 54 hours. For blood and semen, a partial genetic profile was obtained even after 250 hours of UVC radiation in the laminar. When working surfaces were decontaminated with 10% sodium hypochlorite and 20% ethanol, genetic profile could not be obtained for naked DNA after 2 minutes, for saliva after 4 hours, for blood after 16 hours, and for semen after 8 hours of UVC radiation in the laboratory. CONCLUSION: It is recommended to carefully and thoroughly clean working surfaces with 10% sodium hypochlorite and 20% ethanol followed by minimal 16-hour UVC exposure (dose approximately 4380 mJ/cm2) for complete and successful decontamination.

DNA methylation: the future of crime scene investigation?

Proper detection and subsequent analysis of biological evidence is crucial for crime scene reconstruction. The number of different criminal acts is increasing rapidly. Therefore, forensic geneticists are constantly on the battlefield, trying hard to find solutions how to solve them. One of the essential defensive lines in the fight against the invasion of crime is relying on DNA methylation. In this review, the role of DNA methylation in body fluid identification and other DNA methylation applications are discussed. Among other applications of DNA methylation, age determination of the donor of biological evidence, analysis of the parent-of-origin specific DNA methylation markers at imprinted loci for parentage testing and personal identification, differentiation between monozygotic twins due to their different DNA methylation patterns, artificial DNA detection and analyses of DNA methylation patterns in the promoter regions of circadian clock genes are the most important ones. Nevertheless, there are still a lot of open chapters in DNA methylation research that need to be closed before its final implementation in routine forensic casework.