Persistence of DNA in the Singapore context.

The relevance and not merely the presence of one's DNA at a crime scene has become the emerging issue in courtrooms all over the world today. By studying the length of time DNA is likely to persist in an environment until detection, a more holistic assessment of DNA evidence in the context of a case can be made. The current study looks at the persistence of DNA from blood, keratinocytes, and several types of mock exhibits under various conditions, in the tropical rainforest climate of Singapore. While DNA on articles left outdoors showed highly variable persistence subject to the presence of rainfall, DNA from items placed indoors at ambient temperature and under controlled temperature and humidity is comparatively stable. The information gathered from this study, while not exhaustive, serves to provide investigators and the courts with a better understanding of the relevance of DNA recovered from crime scenes of different environmental conditions.

Amplification volume reduction on DNA database samples using FTA™ Classic Cards.

The DNA forensic community always strives towards improvements in aspects such as sensitivity, robustness, and efficacy balanced with cost efficiency. Therefore our laboratory decided to study the feasibility of PCR amplification volume reduction using DNA entrapped in FTA™ Classic Card and to bring cost savings to the laboratory. There were a few concerns the laboratory needed to address. First, the kinetics of the amplification reaction could be significantly altered. Second, an increase in sensitivity might affect interpretation due to increased stochastic effects even though they were pristine samples. Third, statics might cause FTA punches to jump out of its allocated well into another thus causing sample-to-sample contamination. Fourth, the size of the punches might be too small for visual inspection. Last, there would be a limit to the extent of volume reduction due to evaporation and the possible need of re-injection of samples for capillary electrophoresis. The laboratory had successfully optimized a reduced amplification volume of 10 µL for FTA samples.

Sequence polymorphism of the mitochondrial DNA hypervariable regions I and II in 205 Singapore Malays.

Mitochondrial DNA sequences of the hypervariable regions HV1 and HV2 were analyzed in 205 unrelated ethnic Malays residing in Singapore as an initial effort to generate a database for forensic identification purposes. Sequence polymorphism was detected using PCR and direct sequencing analysis. A total of 152 haplotypes was found containing 152 polymorphisms. Out of the 152 haplotypes, 115 were observed only once and 37 types were seen in multiple individuals. The most common haplotype (16223T, 16295T, 16362C, 73G, 146C, 199C, 263G, and 315.1C) was shared by 7 (3.41%) individuals, two haplotypes were shared by 4 individuals, seven haplotypes were shared by 3 individuals, and 27 haplotypes by 2 individuals. Haplotype diversity and random match probability were estimated to be 0.9961% and 0.87%, respectively.

Population study of 11 Y-chromosomal STR loci in Singapore Chinese.

In this study of 212 unrelated Singapore Chinese males, allelic frequencies and gene diversities of 11 Y-chromosome specific STR loci (DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS385a/b, DYS438 and DYS439) were established. A total of 184 haplotypes were observed in the 212 individuals studied, of which 165 (89.67%) were unique. The most common haplotype was observed in five (2.35%) individuals. The overall haplotype diversity for the 11 Y-STR loci was 99.81%, and the discrimination capacity was 86.79%.