http://www.investigativegenetics.com The most accessed research articles published by Investigative Genetics 2012-04-20T00:00:00Z DNA analysis is frequently used to acquire information from biological material to aid enquiries associated with criminal offences, disaster victim identification and missing persons investigations. As the relevance and value of DNA profiling to forensic investigations has increased, so too has the desire to generate this information from smaller amounts of DNA. Trace DNA samples may be defined as any sample which falls below recommended thresholds at any stage of the analysis, from sample detection through to profile interpretation, and can not be defined by a precise picogram amount. Here we review aspects associated with the collection, DNA extraction, amplification, profiling and interpretation of trace DNA samples. Contamination and transfer issues are also briefly discussed within the context of trace DNA analysis. Whilst several methodological changes have facilitated profiling from trace samples in recent years it is also clear that many opportunities exist for further improvements. http://www.investigativegenetics.com/content/1/1/14 Roland van Oorschot Kaye Ballantyne R John Mitchell Investigative Genetics 2010, null:14 2010-12-01T00:00:00Z doi:10.1186/2041-2223-1-14 /content/figures/2041-2223-1-14-toc.gif Investigative Genetics 2041-2223 ${item.volume} 14 2010-12-01T00:00:00Z XML . http://www.investigativegenetics.com/content/3/1/9 Antti Sajantila Investigative Genetics 2012, null:9 2012-04-20T00:00:00Z doi:10.1186/2041-2223-3-9 As a new feature of Investigative Genetics, the Editors-in-Chief will be writing short summaries every other month on interesting research published within the field. This month Prof Sajantila discusses a recently published major breakthrough in the genetics of coronary heart disease and the importance of translational medicine in health research today. /content/figures/2041-2223-3-9-toc.gif Investigative Genetics 2041-2223 ${item.volume} 9 2012-04-20T00:00:00Z PDF Rapid advances in the development of sequencing technologies in recent years have enabled an increasing number of applications in biology and medicine. Here, we review key technical aspects of the preparation of DNA templates for sequencing, the biochemical reaction principles and assay formats underlying next-generation sequencing systems, methods for imaging and base calling, quality control, and bioinformatic approaches for sequence alignment, variant calling and assembly. We also discuss some of the most important advances that the new sequencing technologies have brought to the fields of human population genetics, human genetic history and forensic genetics. http://www.investigativegenetics.com/content/2/1/23 Eva Berglund Anna Kiialainen Ann-Christine Syvanen Investigative Genetics 2011, null:23 2011-11-24T00:00:00Z doi:10.1186/2041-2223-2-23 /content/figures/2041-2223-2-23-toc.gif Investigative Genetics 2041-2223 ${item.volume} 23 2011-11-24T00:00:00Z XML Background: Koreans are generally considered a Northeast Asian group, thought to be related to Altaic-language-speaking populations. However, recent findings have indicated that the peopling of Korea might have been more complex, involving dual origins from both southern and northern parts of East Asia. To understand the male lineage history of Korea, more data from informative genetic markers from Korea and its surrounding regions are necessary. In this study, 25 Y-chromosome single nucleotide polymorphism markers and 17 Y-chromosome short tandem repeat (Y-STR) loci were genotyped in 1,108 males from several populations in East Asia. Results: In general, we found East Asian populations to be characterized by male haplogroup homogeneity, showing major Y-chromosomal expansions of haplogroup O-M175 lineages. Interestingly, a high frequency (31.4%) of haplogroup O2b-SRY465 (and its sublineage) is characteristic of male Koreans, whereas the haplogroup distribution elsewhere in East Asian populations is patchy. The ages of the haplogroup O2b-SRY465 lineages (~9,900 years) and the pattern of variation within the lineages suggested an ancient origin in a nearby part of northeastern Asia, followed by an expansion in the vicinity of the Korean Peninsula. In addition, the coalescence time (~4,400 years) for the age of haplogroup O2b1-47z, and its Y-STR diversity, suggest that this lineage probably originated in Korea. Further studies with sufficiently large sample sizes to cover the vast East Asian region and using genomewide genotyping should provide further insights. Conclusions: These findings are consistent with linguistic, archaeological and historical evidence, which suggest that the direct ancestors of Koreans were proto-Koreans who inhabited the northeastern region of China and the Korean Peninsula during the Neolithic (8,000-1,000 BC) and Bronze (1,500-400 BC) Ages. http://www.investigativegenetics.com/content/2/1/10 Soon-Hee Kim Ki-Cheol Kim Dong-Jik Shin Han-Jun Jin Kyoung-Don Kwak Myun-Soo Han Joon-Myong Song Won Kim Wook Kim Investigative Genetics 2011, null:10 2011-04-04T00:00:00Z doi:10.1186/2041-2223-2-10 /content/figures/2041-2223-2-10-toc.gif Investigative Genetics 2041-2223 ${item.volume} 10 2011-04-04T00:00:00Z XML For much of the 20th century the fate of the last Imperial family of Russia, the Romanovs, was a mystery after their execution in 1918. In the mid 1970s the mass grave of the Romanov family (minus two of the children) was discovered and officially exhumed after the fall of the Soviet Union. Forensic DNA testing of the remains in the early 1990s was used to identify the family. Despite the overwhelming evidence for establishing the identity of the Romanov family, a small but vocal number of scientists have tried to raise doubt about the DNA testing during the late 1990s and early 2000s. With the discovery of the two missing Romanov children in 2007, there was an opportunity to re-analyze all of the evidence associated with the case which confirmed the initial DNA testing and brought finality to the mystery. This article will discuss the controversies associated with the Romanov identification and reflect upon the importance of the case to the field of forensic DNA typing over the last 20 years. http://www.investigativegenetics.com/content/2/1/20 Michael Coble Investigative Genetics 2011, null:20 2011-09-26T00:00:00Z doi:10.1186/2041-2223-2-20 /content/figures/2041-2223-2-20-toc.gif Investigative Genetics 2041-2223 ${item.volume} 20 2011-09-26T00:00:00Z XML The extent of wildlife crime is unknown but it is on the increase and has observable effects with the dramatic decline in many species of flora and fauna. The growing awareness of this area of criminal activity is reflected in the increase in research papers on animal DNA testing, either for the identification of species or for the genetic linkage of a sample to a particular organism. This review focuses on the use of species testing in wildlife crime investigations. Species identification relies primarily on genetic loci within the mitochondrial genome; focusing on the cytochrome b and cytochrome oxidase 1 genes. The use of cytochrome b gained early prominence in species identification through its use in taxonomic and phylogenetic studies, while the gene sequence for cytochrome oxidase was adopted by the Barcode for Life research group. This review compares how these two loci are used in species identification with respect to wildlife crime investigations. As more forensic science laboratories undertake work in the wildlife area, it is important that the quality of work is of the highest standard and that the conclusions reached are based on scientific principles. A key issue in reporting on the identification of a particular species is a knowledge of both the intraspecies variation and the possible overlap of sequence variation from one species to that of a closely related species. Recent data showing this degree of genetic separation in mammalian species will allow greater confidence when preparing a report on an alleged event where the identification of the species is of prime importance. The aim of this review is to illustrate aspects of species testing in wildlife forensic science and to explain how a knowledge of genetic variation at the genus and species level can aid in the reporting of results. http://www.investigativegenetics.com/content/2/1/2 Adrian Linacre Shanan Tobe Investigative Genetics 2011, null:2 2011-01-13T00:00:00Z doi:10.1186/2041-2223-2-2 /content/figures/2041-2223-2-2-toc.gif Investigative Genetics 2041-2223 ${item.volume} 2 2011-01-13T00:00:00Z XML Background: There is substantial ethnic, cultural and linguistic diversity among the people living in east Africa, Sudan and the Nile Valley. The region around the Nile Valley has a long history of succession of different groups, coupled with demographic and migration events, potentially leading to genetic structure among humans in the region.ResultWe report the genotypes of the 15 Identifiler microsatellite markers for 498 individuals from 18 Sudanese populations representing different ethnic and linguistic groups. The combined power of exclusion (PE) was 0.9999981, and the combined match probability was 1 in 7.4 × 1017. The genotype data from the Sudanese populations was combined with previously published genotype data from Egypt, Somalia and the Karamoja population from Uganda. The Somali population was found to be genetically distinct from the other northeast African populations. Individuals from northern Sudan clustered together with those from Egypt, and individuals from southern Sudan clustered with those from the Karamoja population. The similarity of the Nubian and Egyptian populations suggest that migration, potentially bidirectional, occurred along the Nile river Valley, which is consistent with the historical evidence for long-term interactions between Egypt and Nubia. Conclusion: We show that despite the levels of population structure in Sudan, standard forensic summary statistics are robust tools for personal identification and parentage analysis in Sudan. Although some patterns of population structure can be revealed with 15 microsatellites, a much larger set of genetic markers is needed to detect fine-scale population structure in east Africa and the Nile Valley. http://www.investigativegenetics.com/content/2/1/12 Hiba Babiker Carina Schlebusch Hisham Hassan Mattias Jakobsson Investigative Genetics 2011, null:12 2011-05-04T00:00:00Z doi:10.1186/2041-2223-2-12 /content/figures/2041-2223-2-12-toc.gif Investigative Genetics 2041-2223 ${item.volume} 12 2011-05-04T00:00:00Z XML A report on the Swedish Royal Academy of Sciences Symposium on Modern Human Genetic Variation. Stockholm, Sweden. January 19-20, 2012. http://www.investigativegenetics.com/content/3/1/7 Joshua Akey Investigative Genetics 2012, null:7 2012-03-24T00:00:00Z doi:10.1186/2041-2223-3-7 /content/figures/2041-2223-3-7-toc.gif Investigative Genetics 2041-2223 ${item.volume} 7 2012-03-24T00:00:00Z XML . http://www.investigativegenetics.com/content/3/1/8 Mark Jobling Investigative Genetics 2012, null:8 2012-04-16T00:00:00Z doi:10.1186/2041-2223-3-8 The frozen landscape encountered by Mark Jobling during a recent trip to Lausanne, Switzerland has inspired this month's 'Mark my words' column to discuss the miserable fates of those who perish in the snow, using a case study of Otzi the iceman. /content/figures/2041-2223-3-8-toc.gif Investigative Genetics 2041-2223 ${item.volume} 8 2012-04-16T00:00:00Z PDF DNA typing is an important tool in missing-person identification, especially in mass-fatality disasters. Identification methods comparing a DNA profile from unidentified human remains with that of a direct (from the person) or indirect (for example, from a biological relative) reference sample and ranking the pairwise likelihood ratios (LR) is straightforward and well defined. However, for indirect comparison cases in which several members from a family can serve as reference samples, the full power of kinship analysis is not entirely exploited. Because biologically related family members are not genetically independent, more information and thus greater power can be attained by simultaneous use of all pedigree members in most cases, although distant relationships may reduce the power. In this study, an improvement was made on the method for missing-person identification for autosomal and lineage-based markers, by considering jointly the DNA profile data of all available family reference samples. The missing person is evaluated by a pedigree LR of the probability of DNA evidence under alternative hypotheses (for example, the missing person is unrelated or if they belong to this pedigree with a specified biological relationship) and can be ranked for all pedigrees within a database. Pedigree LRs are adjusted for population substructure according to the recommendations of the second National Research Council (NRCII) Report. A realistic mutation model was also incorporated to accommodate the possibility of false exclusion. The results show that the effect of mutation on the pedigree LR is moderate, but LRs can be significantly decreased by the effect of population substructure. Finally, Y chromosome and mitochondrial DNA were integrated into the analysis to increase the power of identification. A program titled MPKin was developed, combining the aforementioned features to facilitate genetic analysis for identifying missing persons. The computational complexity of the algorithms is explained, and several ways to reduce the complexity are introduced. http://www.investigativegenetics.com/content/1/1/8 Jianye Ge Bruce Budowle Ranajit Chakraborty Investigative Genetics 2010, null:8 2010-10-04T00:00:00Z doi:10.1186/2041-2223-1-8 /content/figures/2041-2223-1-8-toc.gif Investigative Genetics 2041-2223 ${item.volume} 8 2010-10-04T00:00:00Z XML