Characterization of the polymorphic repeat sequence within the rDNA IGS of Cannabis sativa

The rDNA intergenic spacer (IGS) structure of Cannabis sativa contains six variable repeat motifs within a locus spanning 1387 base pairs. The degree of variation of the first three motifs was examined using 77 samples from cannabis samples. The samples originated from five seizures in Taiwan and seed stocks from six different countries. The results showed that there were four types of sequences producing PCR products at either 255, 260, 264 or 265 base pairs. The data obtained indicates that this region of rDNA IGS exhibits a degree of polymorphism that while insufficient by itself can be added to a multiplex with other cannabis STR loci.     

Extraction of human DNA for PCR from chewed residues of betel quid using a novel "PVP/CTAB" method

Residues of chewed betel quid (BQ) are often found on crime scenes in Taiwan and possibly some of the Southeast Asian countries. Although these residues are important biological evidences relating to the suspects, the forensic analysis of BQ evidence has been hindered by failures in extraction of human DNA for PCR analysis. Therefore, it is a prerequisite for relevant forensic casework to establish a reliable method for extracting DNA from chewed BQ residues. Three conventional methods (salt/chloroform, 5% Chelex-100 resin, and QIAamp) were first tested for extraction of human DNA from 33 mock BQ samples, which had been stored for less than two months, and 50 four-year-old forensic BQ samples. PCR amplifications from the HLA-DQA1&PM and the STR loci were then used to test the quality of the extracted DNA. For the mock samples, three observations were made. First, PCR amplification of DNA extracted by using these conventional methods had low success rate. Second, the addition of extra Taq DNA polymerase could compensate the lost enzyme activities due to putative inhibitors and, thus, increase the yield. Third, using the Centricon-100 column to remove putative inhibitors substantially improved the efficiency of PCR. However, for the four-year-old forensic BQ samples, none of the attempts for PCR were successful. In order to solve the problem in PCR analysis of DNA from old BQ samples, we developed a DNA extraction method based on the use of polyvinyl pyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB), which bind to two common classes of PCR inhibitors in plants, polyphenols, and polysaccharides, respectively. The result showed that this "PVP/CTAB" method is completely successful for the mock BQ samples, and 92% (46 out of 50) successful for the four-year-old forensic BQ samples. To our best knowledge, this is the first report of a reliable method for the extraction of human DNA for PCR from chewed BQ residues. This method should provide a useful means for forensic identification in countries where betel chewing is common.     

Sequence analysis of STR polymorphisms at locus ACTBP2 in the Taiwanese population

A highly polymorphic sequence structure is reported in the human beta-actin related pseudogene 2 (ACTBP2) (SE33) locus in members of the Taiwanese Han population. A total of 100 unrelated members of the Taiwanese Han population were used in the study. Alleles that shared the same size but differ in their sequence are described to allow for inter laboratory sharing of data. PCR products amplified from this locus were separated by single-strand conformation polymorphism electrophoresis, the single-stranded DNA bands were excised from the gels, a second amplification performed, and then the PCR products were sequenced. All the alleles differed by either 2 or 4 bp. Sequence variations were observed as deletions or insertions in the repeat units AG (or AA) and AAAG. Additionally, transitions in the flanking regions were recorded. A total of 27 alleles with 71 associated genotypes were recorded if the alleles were defined by size, but 68 alleles with 88 associated genotypes were noted with the alleles were scored on the basis of sequence variation. The power of discrimination (Pd) of this single locus was 0.9874 making the human ACTBP2 a good alternative marker for individual identification and paternity testing.     

Forensic applications of infrared imaging for the detection and recording of latent evidence

We report on a simple method to record infrared (IR) reflected images in a forensic science context. Light sources using ultraviolet light have been used previously in the detection of latent prints, but the use of infrared light has been subjected to less investigation. IR light sources were used to search for latent evidence and the images were captured by either video or using a digital camera with a CCD array sensitive to IR wavelength. Bloodstains invisible to the eye, inks, tire prints, gunshot residue, and charred document on dark background are selected as typical matters that may be identified during a forensic investigation. All the evidence types could be detected and identified using a range of photographic techniques. In this study, a one in eight times dilution of blood could be detected on 10 different samples of black cloth. When using 81 black writing inks, the observation rates were 95%, 88% and 42% for permanent markers, fountain pens and ball-point pens, respectively, on the three kinds of dark cloth. The black particles of gunshot residue scattering around the entrance hole under IR light were still observed at a distance of 60 cm from three different shooting ranges. A requirement of IR reflectivity is that there is a contrast between the latent evidence and the background. In the absence of this contrast no latent image will be detected, which is similar to all light sources. The use of a video camera allows the recording of images either at a scene or in the laboratory. This report highlights and demonstrates the robustness of IR to detect and record the presence of latent evidence.     

The Relationship between Homelessness and Behavior Problems among Youth in North Texas: a Brief Report

This study sought to examine the relationship between homelessness and behavior problems among a community-based sample of youth in North Texas. Data were obtained from a cross-sectional, probability sample of households and a targeted sample of homeless families in Dallas, Texas, with children older than 5 years old (N?=?5232). Parents were asked to report five behavior problems on behalf of their children including arrest or trouble with police, academic problems, behavior problems at school, suspension, and suicide attempts. Logistic and negative binomial regression procedures were used to examine the relationship between homelessness and behavior problems. Youth exposed to homelessness were 36% (OR?=?1.63; 95% CI 1.00–1.85) more likely to exhibit any kind of behavior problems than youth who had never experienced homelessness. Homeless youth had 5.51 times the odds of arrest (95% CI 2.60–11.68), 1.74 times the odds of academic problems (95% CI 1.24–2.43), and more than 3 times the odds of suicide attempts (95% CI 1.46, 7.61) than youth who had never been homeless. Homelessness was associated with higher rates of problem behavior, including arrests, academic problems, and suicide attempts. Because homeless youth are commonly enrolled in school and present at health care clinics and emergency departments, clinics and schools may aid in the identification of homeless youth, as well as referral to care. In this way, clinicians may help reduce the burden of behavioral problems that disproportionately affect homeless youth.