The use of genetic materials, RNA, to determine the age of saliva stains

• Main Author: Alrowaithi, Majid A.
• Published: University of Strathclyde 2013
• Subjects: 540
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.605929

DNA analysis, it does not provide any information about the time of the deposition of biological stain. In this work, the relationship between the age of the saliva stains that were aged for specific periods of time and the degradation rate of specific RNA molecules were assessed to find the correlation between them. Two types of approaches and two types of RNA molecules were used for this purpose. In the first approach, the relationship assessment was carried out between the saliva's age and the relative quantity ratio (RQR) of two species of the housekeeping genes (β-actin mRNA and 18S rRNA) that were used in a previous study assessed on bloodstains. In the second pilot approach, the relationship assessment was carried out between the saliva's age and the relative quantities of two different-sized segments on the same saliva-specific mRNA markers quantified were assessed with using a pair of TaqMan® Gene Expression Assays (TGEAs). Correlations were found between the age of the saliva stain and the RQR of the β-actin mRNA to 18S rRNA in the first approach and between the age of the saliva stains and the relative quantities of two different-sized segments of some saliva-specific mRNA markers in the second approach and the age of the sample can be approximated by both. In addition, use of saliva-specific RNA in the second approach offers the advantage of simultaneous age determination and body fluid identification for both saliva and blood. In addition factors affecting the determination of the age of biological stains by means of the analysis of ribonucleic acids such as mixture status, using of RNAlater® stabiliser, were also evaluated. Finally, methods that may be employed to apply the findings to casework, taking into account the level of accuracy achieved, are discussed.