The Y chromosome and its use in forensic DNA analysis

Originally relatively ignored in forensic investigations because its genetic analysis lacks inference of individual identification, the value of Y chromosome analysis has been proven in cases of sexual assault, particularly where the amount of material left by a male assailant is limited in comparison with female DNA. All routine analysis of autosomal DNA, however, targets a gene (AMELY) on the Y chromosome in order to identify the sex of the DNA source and this is discussed in the context of the genetic structure of this male-specific chromosome. Short-tandem repeat markers on the chromosome are tested in dedicated multiplexes that have developed over time and these are described alongside international guidance as to their use in a forensic setting. As a marker of lineage, the Y chromosome provides additional tools to assist in the inference of ancestry, both geographical and familial and the value of Y chromosome testing is illustrated through descriptions of cases of criminal and historical interest. A decision to analyse the Y chromosome has to be considered in the context, not only of the circumstances of the case, but also with regard to the ethical questions it might raise, and these are discussed in relation to the cases that have been described in more detail in the accompanying online supplementary material.

Methylenetetrahydrofolate Reductase Dimer Configuration as a Risk Factor for Maternal Meiosis I-Derived Trisomy 21

<b><i>Background:</i></b> Evidence suggests that the dimer configuration of methylenetetrahydrofolate reductase (MTHFR) enzyme might be destabilized by polymorphisms in monomers at the positions C677T and A1298C. It has been observed that these polymorphisms may lead to stable (CCAA, CCAC, CCCC) and unstable (CTAA, CTAC, TTAA) enzyme dimer configurations. <b><i>Objective:</i></b> The aim of this study was to evaluate the association of the MTHFR enzyme dimer configuration and folate dietary intake with the stage of meiotic nondisjunction in mothers of children with maternally derived trisomy 21. <b><i>Methods:</i></b> A total of 119 mothers of children with maternally derived free trisomy 21 were included in the study. The mean maternal age at the time of the birth of the child with trisomy 21 was 32.3 ± 6.4 (range 16–43) years. All mothers were Caucasian. Parental origin of trisomy 21 and meiotic stage of nondisjunction was determined using short tandem repeat markers spanning from the centromere to the telomere of chromosome 21q. The <i>MTHFR</i> C677T and <i>A1298C</i> polymorphism was evaluated by PCR-RFLP. <b><i>Results:</i></b> Increased frequency of the <i>MTHFR</i> genotype combinations CTAA, CTAC, and TTAA was found in the group of mothers with meiosis I (MI) nondisjunction (<i>p</i> = 0.007). No differences were found between study participants regarding dietary and lifestyles habits. <b><i>Conclusion:</i></b> The risk for MI nondisjunction of chromosome 21 was 4.6-fold higher in cases who had CTAA, CTAC, and TTAA <i>MTHFR</i> genotype combinations and who did not used folic acid supplements in the preconception period.

Population genetics and forensic utility of 23 autosomal PowerPlex Fusion 6C STR loci in the Kuwaiti population

This study evaluates the forensic utility of 23 autosomal short tandem repeat markers in 400 samples from the Kuwaiti population, of which four markers (D10S1248, D22S1045, D2S441 and SE33) are reported for the first time for Kuwait. All the markers were shown to exhibit no deviation from Hardy–Weinberg equilibrium, nor any linkage disequilibrium between and within loci, indicating that these loci are inherited independently, and their allele frequencies can be used to estimate match probabilities in the Kuwaiti population. The low combined match probability of 7.37 × 10–30 and the high paternity indices generated by these loci demonstrate the usefulness of the PowerPlex Fusion 6C kit for human identification in this population, as well as to strengthen the power of paternity testing. Off-ladder alleles were seen at several loci, and these were identified by examining their underlying nucleotide sequences. Principal component analysis (PCA) and STRUCTURE showed no genetic structure within the Kuwaiti population. However, PCA revealed a correlation between geographic and genetic distance. Finally, phylogenetic trees demonstrated a close relationship between Kuwaitis and Middle Easterners at a global level, and a recent common ancestry for Kuwait with its northern neighbours of Iraq and Iran, at a regional level.

Authentication of the green monkey kidney Vero76 cell lines subcultured through many generations

The Vero76 cell lines isolated from the kidney of an African green monkey (Chlorocebus aethiops sabaeus), are commonly used for viral culture, vaccine development, and cytotoxicity assays. However, subculturation of cell lines over multiple generations can lead to a genetic change in these cell lines compared to the original cell. This will lead to deviations in results of research that using the modified cell lines. Therefore, identification and evaluation periodically the genetic stability of cell lines after subculture are necessary. In recently studies, cell authentication by using STR markers (short tandem repeat markers) have been becoming a simple and effective method that used commonly. In this study, we used eight STR markers: D17S1304, D5S1467, D19S245, D1S518, D8S1106, D4S2408, D6S1017, and DYS389 for cell lines authentication and evaluation of the genetic stability of subcultured Vero76 cell lines. The STR indicators were amplified, sequenced and compared with the original cell to identify the differences between cell lines in subcultured generations. The evaluation results showed that these cell lines did not have any differ compared with the original cell line, this confirmed that the genetic of the cell lines were stability. The results also suggested that STR markers can be used to authenticate for Vero76 cell lines.

Genetic Diversity and Population Structure of Dromedary Camel-Types

The dromedary camel is a unique livestock for its adaptations to arid-hot environments and its ability to provide goods under extreme conditions. There are no registries or breed standards for camels. Thus, named camel populations (i.e., camel-types) were examined for genetic uniqueness and breed status. Camel populations are generally named based on shared phenotype, country or region of origin, tribal ownership, or the ecology of their habitat. A dataset of 10 Short-Tandem Repeat markers genotyped for 701 individual camels from 27 camel-types was used to quantify genetic diversity within camel-types, compare genetic diversity across camel-types, determine the population genetic structure of camel-types, and identify camel-types that may represent true breeds. Summary statistics (genotyping call rate, heterozygosity, inbreeding coefficient FIS, and allelic frequencies) were calculated and population-specific analyses (pairwise FST, neighbor-joining tree, relatedness, Nei’s genetic distance, principal coordinate analysis [PCoA], and STRUCTURE) were performed. The most notable findings were 1) little variation in genetic diversity was found across the camel-types, 2) the highest genetic diversity measure was detected in Targui and the lowest was in Awarik, 3) camel-types from Asia (especially the Arabian Peninsula) exhibited higher genetic diversity than their counterparts in Africa, 4) the highest DeltaK value of population structure separated camel-types based on geography (Asia vs. Africa), 5) the most distinct camel-types were the Omani, Awarik, and the Gabbra, 6) camel-types originating from the same country did not necessarily share high genetic similarity (e.g., camel-types from Oman), and 7) camel-type names were not consistently indicative of breed status.