Genetic polymorphism at 15 tetrameric short tandem repeat loci in four aboriginal tribal populations of Bengal

POPULATIONS: This study reports the genetic polymorphism observed at 15 short tandem repeat loci D3S1358, TH01, D21S11, D18S51, D5S818, D13S317, D7S820, D16S539, CSF1PO, vWA, D8S1179, TPOX, D2S1338, D19S433, and FGA in four aboriginal populations of Bengal. The analysis was performed to decipher the suitability of CODIS as well as six other highly polymorphic and unlinked markers in Forensic Testing. Studied populations include four tribes: Karmali, Kora, Maheli, and Lodha.     

An evaluation of matching unknown writing inks with the United States International Ink Library

Utilizing a database of standards for forensic casework is a valuable resource. Undoubtedly, as more standards (and corresponding information about the specimens) are collected, there is a greater certainty of identification when a questioned and a known item cannot be distinguished after a series of analyses. The United States Secret Service and the Internal Revenue Service National Forensic Laboratory jointly maintain the largest known forensic collection of writing inks in the world, which is comprised of over 8500 ink standards collected worldwide, dating back to the 1920s. This study was conducted to evaluate the reliability of matching arbitrarily purchased pens with known inks from a database. One hundred pens were randomly obtained from a variety of sources and their respective ink compositions were compared with standards. Eighty-five of the inks were determined to be suitable for comparison utilizing optical examinations and thin-layer chromatography. Three of the inks did not match any of the specimens on record; one of these inks was similar to an ink from an identical brand of pen that was in the database, but had a modified formulation.     

A simple and inexpensive molecular method for sexing and identification of the forensic samples of elephant origin

The population of the Asian elephant is being dramatically reduced due to poaching of the ivory from the male. As poaching occurs in remote forests, it often takes weeks or longer for it to be discovered and it is therefore often very difficult to determine the sex of the decomposed body. Data suggest that in the recent past, over 2000 male elephants have been poached in South India. We have developed a technique based on molecular markers to determine that the carcass is an elephant and that it is a male. Using DNA sequence information from Genbank, we have developed two primer pairs: one for the mitochondrial DNA (mtDNA) and the other for the sex-determining region of Y chromosome (SRY) gene of the Indian elephant. After PCR amplification of known elephant DNA, we found that the mtDNA was common in both males and females, whereas the SRY-specific amplicon was observed only in the male.     

Fatal bromethalin poisoning

Bromethalin is a neurotoxin found in some rodenticides. A delusional 21-year-old male presented to a hospital with altered mental status the day after ingesting a bromethalin-based rodenticide. He died 7 days after his self-reported exposure to c. 17 mg bromethalin (equivalent to 0.33 mg bromethalin/kg). His clinicopathologic course was characterized by altered mental status, obtundation, increased cerebrospinal fluid pressure, cerebral edema, death, and diffuse histologic vacuolization of the white matter in the central nervous system seen on microscopic examination at autopsy. The presence of a demethylated form of bromethalin in the patient's liver and brain was confirmed by gas chromatography with mass spectrometry. Clinical signs and lesions observed in this patient are similar to those seen in animals poisoned with bromethalin. This case illustrates the potential for bromethalin ingestion to result in fatal human poisoning.     

Metric assessment of the "mastoid triangle" for sex determination: a validation study

Recently, a metric approach to skeletal sex determination was published by Paiva and Segre which is based on the summation of two triangular areas defined by three distinct craniometric landmarks: Porion, Mastoidale, and Asterion. According to the authors, values for the total triangle > or =1447.40 mm(2) are characteristic for male crania, while values < or =1260.36 mm(2) are indicative of female skulls (95% confidence). In order to evaluate the method's validity, two sex- and age-documented samples of different provenience were analyzed (N=197). The results show that while the indicated measurements display significant sex differences, the technique is of little practical meaning where a single individual must be independently classified. It is hypothesized that differences in the expression of sexual dimorphism as well as a population-specific variability of the asterion location undermine the value of the mastoid triangle as a sex determinant.     

Characterization of the N+3 stutter product in the trinucleotide repeat locus DYS392

Stutter products generated during DNA amplification by the polymerase chain reaction (PCR) may complicate mixture interpretation. The PCR amplification of the DYS392 locus typically results in three distinct detectable PCR products: the true allele product (N), a stutter product three bases smaller (N-3), and a reproducible low-level product, three bases larger (N+3). Sequence analysis of the N+3 product demonstrated that its sequence is one TAT repeat longer than the true allele product. Our experiments demonstrated that the quantity of both N-3 and N+3 stutter increased as the allele number increased. The percent stutter also increased as the magnesium concentration was increased in the reaction, as well as when the amount of input DNA was decreased. As both stutter products behave in a similar and reproducible fashion, the same rules that apply to the interpretation of N-3 stutter products in short tandem repeat analysis, can be applied to N+3 stutters. The characterization of the DYS392 N+3 product is the first detailed published study of a stutter product larger than the true allele.