Funded by: PCHRD
Project Leader: Maria Corazon A. de Ungria, PHD
Forensic DNA profiling has been used to assist in criminal investigations and resolution of civil disputes, such as filiation testing and to aid in disaster victim identification (DVI). In the last 10 years, advances in the field of DNA forensics has significantly increased the standards of resolving questions of human identity that are used as evidence in courts worldwide.
For scientific evidence such as DNA analysis to be admitted before Philippine courts, it must be demonstrated that the methods used have been tested empirically and subjected to peer review and publication. Nowadays, the basic science behind the use of DNA analysis for human identification and relationship testing is rarely called into question in court. Instead, questions focus on the validity of the techniques used and the capability of the laboratory that performed the analysis. Thus, to ensure the acceptance of forensic DNA technology in the Philippines, the effectivity of the technology in providing objective answers to questions of human identification and relationship testing must be demonstrated in the local setting.
Project 1: Human Remains Identification and DNA Profiling
Duration of the Project: 15 January 2013 – 14 October 2016
Source of Fund: DOST-PCHRD
Project Leader: Gayvelline C. Calacal, RMT, MSc
Position/Agency: Scientist I, DOST/CSC Scientific Career System, University Researcher II, DNA Analysis Laboratory, NSRI, UP Diliman, Quezon City
In cases of disaster victim identification, missing persons and other forensic investigations involving human remains identification, samples encountered may have been exposed to various environmental conditions such as extreme heat, water immersion, burial, chemical treatment and post mortem decomposition. Such conditions can cause significant DNA resulting to fragmentation and degradation, which in turn may lead to negative DNA profiling results or the generation of only partial genetic profiles.
In this study, we established validated procedures for the analysis of degraded human samples for forensic applications. It focused on different factors that affect the success of DNA-based human identification in disaster situations. The project included the determination of the robustness and sensitivity of current autosomal STR (aSTR) and Y-STR DNA genotyping and mitochondrial DNA sequencing procedures, the simulation of DNA amplification in the presence of inhibitors and/or chemicals that degrade DNA and the assessment of the quality of DNA profiles after the amplification of DNA that was obtained from biological samples that were exposed to different environmental conditions.
Project 2: Y-Chromosomal DNA Variation of Filipinos across Families Using Rapidly Mutating (RM) Y-chromosome Specific Short Tandem Repeat (STR) Markers
Duration of the Project: 15 January 2013 – 14 January 2016
Source of Fund: DOST-PCHRD
Project Leader: Maria Corazon A. De Ungria, BSc(Honors), PhD
Position/Agency: Scientist II, DOST/CSC Scientific Career System, University Researcher V and Head, DNA Analysis Laboratory, NSRI, UP Diliman; Director, Program on Forensics and Ethnicity, PGC
DNA typing of male-specific polymorphisms on the non-recombining portion of the Y-chromosome, specifically short tandem repeat (STR) loci, is used for male identification. However, the current Y-STR marker sets used in forensic DNA typing provide limited resolution to paternally-related males, and those who belong to small communities wherein in breeding is common. In a previous study by Ballantyne et al, a set of 13 Y-STR loci with very high mutation rate (6.5-fold higher than current Y-STR loci) were identified and termed rapidly mutating (RM) Y-STRs. A subsequent study showed that this set of RM Y-STRs can differentiate male relatives. This project tested the new set of RM Y-STRs in the Philippine population for up to two meiotic events in order to assess the nature and degree of variation in these markers, as well as their capacity to differentiate paternally-related males. Blood samples were collected from 154 paternal lineages composed of 141 father-son1-son2 and 13 grandfather-father-son trios. DNA typing experiments were conducted using a commercially available kit (Powerplex® Y23) that includes a conventional panel of Y-STR markers, and a protocol for amplification at the 13 RM Y-STRs by Ballantyne and co-workers. The DNA profile of one member from each of the family trios was added to the expanded Philippine Y-STR DNA database (n=299). Population genetic analysis of the expanded database revealed high genetic diversities of the RM Y-STR markers in the Philippine population, signifying their utility in differentiating related male persons. Pair wise allele comparison was done for the YSTR data of the family trios in order to identify and count allelic losses or gains. The mutation rates for the 34 Y-STR markers (or 36 Y-STR marker units) estimated in this study among Filipino families reflects the higher mutation rate of the RM Y-STRs compared to conventional Y-STRs as stated in worldwide studies. Comparison of conventional and RM Y-STR haplotypes of paternal pairs (father-son, grandfather-grandson, and brothers) revealed that RM Y-STR markers can distinguish more paternal pairs than conventional Y-STR markers.