Jefferson fathered slave's last child

Forensic investigative genetic genealogy: expanding pedigree tracing and genetic inquiry in the genomic era

Genetic genealogy provides crucial insights into the complex biological relationships within contemporary and ancient human populations by analyzing shared alleles and chromosomal segments that are identical by descent to understand kinship, migration patterns, and population dynamics. Within forensic science, forensic investigative genetic genealogy (FIGG) has gained prominence by leveraging next-generation sequencing technologies and population-specific genomic resources, opening useful investigative avenues. In this review, we synthesize current knowledge, underscore recent advancements, and discuss the growing role of FIGG in forensic genomics. FIGG has been pivotal in revitalizing dormant inquiries and offering genetic leads in numerous cold cases. Its effectiveness relies on the extensive single-nucleotide polymorphism profiles contributed by individuals from diverse populations to specialized genomic databases. Advances in computational genomics and the growth of human genomic databases have spurred a profound shift in the application of genetic genealogy across forensics, anthropology, and ancient DNA studies. As the field progresses, FIGG is evolving from a nascent practice into a more sophisticated and specialized discipline, shaping the future of forensic investigations.

Evaluating genome-wide and targeted forensic sequencing approaches to kinship determination

Kinship determination is a valuable tool in forensic genetics, with applications including familial searching, disaster victim identification, and investigative genetic genealogy. Conventional typing of small numbers of autosomal short tandem repeats (STRs) confidently identifies only first-degree relatives. Massively parallel sequencing (MPS) can access more STRs and resolve alleles identical by length but differing in sequence (isoalleles), which may increase the power of kinship estimation, particularly when combined with additional sequenced single nucleotide polymorphism (SNP) loci, as in the ForenSeq DNA Signature Prep kit. MPS sequencing of ∼10,000 SNPs is available in the ForenSeq Kintelligence kit, promising detection of more distant kin, while SNP chips carrying hundreds of thousands of markers increase resolution still further. Here we evaluate these different resolutions in a set of pedigrees, and via simulations. As expected, the key factor influencing the precision of kinship estimation is the number of markers analysed and MPS-based analysis of STRs increases resolution, with the full set of ForenSeq DNA Signature Prep kit markers allowing detection of third-degree relatives. Since SNP chips include non-autosomal (X- and Y-chromosomal, and mitochondrial [mtDNA]) markers, we ask how these perform within the pedigrees, cross-referencing to Y-STR sequence data. We highlight the importance of understanding haplogroup resolutions in the increasingly complex Y and mtDNA phylogenies, to avoid false exclusions. Incorporation of X-SNPs allows tracing of X-chromosome segments within families. These different approaches can add value to kinship estimation, but some require simpler bioinformatic interfaces to make them more widely accessible in practice, and also access to appropriate allele frequency data to avoid problems associated with ancestry mis-specification.

Guidelines for genetic ancestry inference created through roundtable discussions

The use of genetic and genomic technology to infer ancestry is commonplace in a variety of contexts, particularly in biomedical research and for direct-to-consumer genetic testing. In 2013 and 2015, two roundtables engaged a diverse group of stakeholders toward the development of guidelines for inferring genetic ancestry in academia and industry. This report shares the stakeholder groups' work and provides an analysis of, commentary on, and views from the groundbreaking and sustained dialogue. We describe the engagement processes and the stakeholder groups' resulting statements and proposed guidelines. The guidelines focus on five key areas: application of genetic ancestry inference, assumptions and confidence/laboratory and statistical methods, terminology and population identifiers, impact on individuals and groups, and communication or translation of genetic ancestry inferences. We delineate the terms and limitations of the guidelines and discuss their critical role in advancing the development and implementation of best practices for inferring genetic ancestry and reporting the results. These efforts should inform both governmental regulation and self-regulation.

Revisiting informed consent in forensic genomics in light of current technologies and the times

Informed consent is based on basic ethical principles that should be considered when conducting biomedical and behavioral research involving human subjects. These principles-respect, beneficence, and justice-form the foundations of informed consent which in itself is grounded on three fundamental elements: information, comprehension, and voluntary participation. While informed consent has focused on human subjects and research, the practice has been adopted willingly in the forensic science arena primarily to acquire reference samples from family members to assist in identifying missing persons. With advances in molecular biology technologies, data mining, and access to metadata, it is important to assess whether the past informed consent process and in particular associated risks are concomitant with these increased capabilities. Given the state-of-the-art, areas in which informed consent may need to be modified and augmented are as follows: reference samples from family members in missing persons or unidentified human remains cases; targeted analysis of an individual(s) during forensic genetic genealogy cases to reduce an investigative burden; donors who provide their samples for validation studies (to include population studies and entry into databases that would be applied to forensic statistical calculations) to support implementation of procedures and operations of the forensic laboratory; family members that may contribute samples or obtain genetic information from a molecular autopsy; and use of medical and other acquired samples that could be informative for identification purposes. The informed consent process should cover (1) purpose for collection of samples; (2) process to analyze the samples (to include type of data); (3) benefits (to donor, target, family, community, etc. as applicable); (4) risks (to donor, target, family, community, etc. as applicable); (5) access to data/reports by the donor; (6) sample disposition; (7) removal of data process (i.e., expungement); (8) process to ask questions/assessment of comprehension; (9) follow-up processes; and (10) voluntary, signed, and dated consent. Issues surrounding these topics are discussed with an emphasis on addressing risk factors. Addressing informed consent will allow human subjects to make decisions voluntarily and with autonomy as well as secure the use of samples for intended use.

Genetic diversity of 23 Y-STR loci of the Lisu ethnic minority residing in Chuxiong Yi Autonomous Prefecture, Yunnan province, Southwest China

BACKGROUND

The Lisu group is a unique minority in Yunnan province. However, there is a lack of Y-STR population data for Chinese Lisu and the genetic structure of the Lisu group and other populations is unclear.

AIM

To provide genetic data for 23 Y-STRs in the Chinese Lisu population from Chuxiong Yi Autonomous Prefecture, as well as to analyse population genetic relationships between Chinese Lisu ethnic minority and other reference groups.

SUBJECTS AND METHODS

423 unrelated healthy Lisu males were genotyped using the PowerPlex® Y23 system. Forensic parameters were calculated according to the previously published studies. Genetic structure analysis among Chinese Lisu and other populations was conducted using the YHRD's AMOVA tools.

RESULTS

Gene diversity (GD) ranged from 0.2,466 (DYS438) to 0.8,945 (DYS385a/b) among the 23 Y-STR loci. According to haplotype analysis, 323 different haplotypes were obtained, out of which 271 were unique. The haplotype diversity (HD) and discrimination capacity (DC) were 0.9,977 and 0.7,636, respectively. MDS plot indicated that the Chuxiong Lisu group is genetically related to the Yunnan Yi group.

CONCLUSIONS

This is the first report on Y-STR population data for the Chinese Lisu population. These data would be valuable for forensic applications.

Limited Effect of Y Chromosome Variation on Coronary Artery Disease and Mortality in UK Biobank-Brief Report

BACKGROUND

The effect of genetic variation in the male-specific region of the Y chromosome (MSY) on coronary artery disease and cardiovascular risk factors has been disputed. In this study, we systematically assessed the association of MSY genetic variation on these traits using a kin-cohort analysis of family disease history in the largest sample to date.

METHODS

We tested 90 MSY haplogroups against coronary artery disease, hypertension, blood pressure, classical lipid levels, and all-cause mortality in up to 152 186 unrelated, genomically British individuals from UK Biobank. Unlike previous studies, we did not adjust for heritable lifestyle factors (to avoid collider bias) and instead adjusted for geographic variables and socioeconomic deprivation, given the link between MSY haplogroups and geography. For family history traits, subject MSY haplogroups were tested against father and mother disease as validation and negative control, respectively.

RESULTS

Our models find little evidence for an effect of any MSY haplogroup on cardiovascular risk in participants. Parental models confirm these findings.

CONCLUSIONS

Kin-cohort analysis of the Y chromosome uniquely allows for discoveries in subjects to be validated using family history data. Despite our large sample size, improved models, and parental validation, there is little evidence to suggest cardiovascular risk in UK Biobank is influenced by genetic variation in MSY.

Genealogy: The Tree Where History Meets Genetics

Although biological relationships are a universal reality for all human beings, the concepts of “family” and “family bond” depend on both the geographic region and the historical moment to which they refer. However, the concept of “family” can be determinant in a large variety of societies, since it can influence the lines of succession, inheritances and social relationships, as well as where and with whom an individual is buried. The relation between a deceased person and other members of a community, other individuals of the same necropolis, or even with those who are buried in the same tomb can be analysed from the genetic point of view, considering different perspectives: archaeological, historical, and forensic. In the present work, the concepts of “family” and “kinship” are discussed, explaining the relevance of genetic analysis, such as nuclear and lineage markers, and their contribution to genealogical research, for example in the heritage of surnames and Y-chromosome, as well as those cases where some discrepancies with historical record are detected, such as cases of adoption. Finally, we explain how genetic genealogical analyses can help to solve some cold cases, through the analysis of biologically related relatives.

Perceiving gender while perceiving language: Integrating psycholinguistics and gender theory

There is a substantial body of literature showing that men and women speak differently and that these differences are endemic to the speech signal. However, the psycholinguistic mechanisms underlying the integration of social category perception and language are still poorly understood. Speaker attributes such as emotional state, age, sex, and race have often been treated in the literature as dissociable, but perceptual systems for social categories demonstrably rely on interdependent cognitive processes. We introduce a diversity science framework for evaluating the existing literature on gender and speech perception, arguing that differences in beliefs about gender may be defined as differences in beliefs about differences. Treating individual, group, and societal level contrasts in ideological patterns as phenomenologically distinctive, we enumerate six ideological arenas which define claims about gender and examine the literature for treatment of these issues. We argue that both participants and investigators predictably show evidence of differences in ideological attitudes toward the normative definition of persons. The influence of social knowledge on linguistic perception therefore occurs in the context of predictable variation in both attention and inattention to people and the distinguishing features which mark them salient as kinds. We link experiences of visibility, invisibility, and hypervisibility with ideological variation regarding the significance of physiological, linguistic, and social features, concluding that gender ideologies are implicated both in linguistic processing and in social judgments of value between groups. We conclude with a summary of the key gaps in the current literature and recommendations for best practices studies that may use in future investigations of socially meaningful variation in speech perception. This article is categorized under: Linguistics > Language in Mind and Brain Psychology > Language Linguistics > Language Acquisition Psychology > Perception and Psychophysics.

Human biological variation and the "normal"

Anatomically modern human being is a relatively young species (~300 000 years old) with small amounts of genetic variation contained within them. The vast majority of its existence was spent in Eastern Africa, migration out of the region began around 100 000 YBP. Sub-Saharan African populations have the greatest amount of human genetic variation. However, migration allowed populations to accumulate genomic variation associated with living in the arctic, higher altitudes, disease resistance, living on high fat or starchy foods, surviving toxic arsenic-rich environments, lactase persistence, changing skin pigmentation, gaining thicker hair, and changing height and body mass index. Understanding these aspects of human evolution forces us to reconsider our notion of the "normal." Thus, normal for our species includes having dark melanic skin, brown eyes, and brown tightly curled hair. Derived features include lighter skin (~10 000 YBP), blue eyes (~6000 YBP), and blond straight hair (~6000 YBP). Yet in reality, "normal" has no meaning for a species that inhabits such a broad geographic range. Natural selection and genetic drift have genetically differentiated human populations in ways that impact our morphological and physiological traits. The genomic differentiation is small and does not allow any unambiguous classification of human populations into biological races. Despite these now well-established facts of human variation, significant confusion associated with Eurocentric notions of the normal still persist in both the lay public and various professions such as biomedical research and clinical practice.

Molecular genealogy of Tusi Lu's family reveals their paternal relationship with Jochi, Genghis Khan's eldest son

Genghis Khan's lineage has attracted both academic and general interest because of its mystery and large influence. However, the truth behind the mystery is complicated and continues to confound the scientific study. In this study, we surveyed the molecular genealogy of Northwestern China's Lu clan who claim to be the descendants of the sixth son of Genghis Khan, Toghan. We also investigated living members of the Huo and Tuo clans, who, according to oral tradition, were close male relatives of Lu clan. Using network analysis, we found that the Y-chromosomal haplotypes of Lu clan mainly belong to haplogroup C2b1a1b1-F1756, widely prevalent in Altaic-speaking populations, and are closely related to the Tore clan from Kazakhstan, who claim to be the descendants of the first son of Genghis Khan, Jochi. The most recent common ancestor of the special haplotype cluster that includes the Lu clan and Tore clan lived about 1000 years ago (YA), while the Huo and Tuo clans do not share any Y lineages with the Lu clan. In addition to the reported lineages, such as C3*-Star Cluster, R1b-M343, and Q, our results indicate that haplogroup C2b1a1b1-F1756 might be another candidate of the true Y lineage of Genghis Khan.

Next Generation Sequencing Plus (NGS+) with Y-chromosomal Markers for Forensic Pedigree Searches

There is high demand for forensic pedigree searches with Y-chromosome short tandem repeat (Y-STR) profiling in large-scale crime investigations. However, when two Y-STR haplotypes have a few mismatched loci, it is difficult to determine if they are from the same male lineage because of the high mutation rate of Y-STRs. Here we design a new strategy to handle cases in which none of pedigree samples shares identical Y-STR haplotype. We combine next generation sequencing (NGS), capillary electrophoresis and pyrosequencing under the term ‘NGS+’ for typing Y-STRs and Y-chromosomal single nucleotide polymorphisms (Y-SNPs). The high-resolution Y-SNP haplogroup and Y-STR haplotype can be obtained with NGS+. We further developed a new data-driven decision rule, FSindex, for estimating the likelihood for each retrieved pedigree. Our approach enables positive identification of pedigree from mismatched Y-STR haplotypes. It is envisaged that NGS+ will revolutionize forensic pedigree searches, especially when the person of interest was not recorded in forensic DNA database.

Human Y-chromosome variation in the genome-sequencing era

The properties of the human Y chromosome - namely, male specificity, haploidy and escape from crossing over - make it an unusual component of the genome, and have led to its genetic variation becoming a key part of studies of human evolution, population history, genealogy, forensics and male medical genetics. Next-generation sequencing (NGS) technologies have driven recent progress in these areas. In particular, NGS has yielded direct estimates of mutation rates, and an unbiased and calibrated molecular phylogeny that has unprecedented detail. Moreover, the availability of direct-to-consumer NGS services is fuelling a rise of 'citizen scientists', whose interest in resequencing their own Y chromosomes is generating a wealth of new data.

Forensic use of Y-chromosome DNA: a general overview

The male-specific part of the human Y chromosome is widely used in forensic DNA analysis, particularly in cases where standard autosomal DNA profiling is not informative. A Y-chromosomal gene fragment is applied for inferring the biological sex of a crime scene trace donor. Haplotypes composed of Y-chromosomal short tandem repeat polymorphisms (Y-STRs) are used to characterise paternal lineages of unknown male trace donors, especially suitable when males and females have contributed to the same trace, such as in sexual assault cases. Y-STR haplotyping applied in crime scene investigation can (i) exclude male suspects from involvement in crime, (ii) identify the paternal lineage of male perpetrators, (iii) highlight multiple male contributors to a trace, and (iv) provide investigative leads for finding unknown male perpetrators. Y-STR haplotype analysis is employed in paternity disputes of male offspring and other types of paternal kinship testing, including historical cases, as well as in special cases of missing person and disaster victim identification involving men. Y-chromosome polymorphisms are applied for inferring the paternal bio-geographic ancestry of unknown trace donors or missing persons, in cases where autosomal DNA profiling is uninformative. In this overview, all different forensic applications of Y-chromosome DNA are described. To illustrate the necessity of forensic Y-chromosome analysis, the investigation of a prominent murder case is described, which initiated two changes in national forensic DNA legislation both covering Y-chromosome use, and was finally solved via an innovative Y-STR dragnet involving thousands of volunteers after 14 years. Finally, expectations for the future of forensic Y-chromosome DNA analysis are discussed.

Whose History?

This article examines the contested versions of history, defined as a kind of discourse, surrounding the attempt to establish a museum in Tampa, Florida. As part of a strategy of urban redevelopment, white elites in Tampa in the early 1990s attempted to attract a museum with a piracy theme based on artefacts recovered from The Whydah Galley, an 18th-century pirate ship — the piracy image fitting well with their own `invented tradition'. However, when it was discovered that the ship was originally used in the slave trade, local African American civic leaders mounted a protest, using a counter-discourse that challenged interpretations of `history' by addressing issues of identity, partially through references to slavery and utilizing a rhetoric of cultural authenticity, questioning the elites' cultural and class ascendancy. The project was eventually cancelled.

The Sequence and Structure Determine the Function of Mature Human miRNAs

Micro RNAs (miRNAs) (19–25 nucleotides in length) belong to the group of non-coding RNAs are the most abundant group of posttranscriptional regulators in multicellular organisms. They affect a gene expression by binding of fully or partially complementary sequences to the 3’-UTR of target mRNA. Furthermore, miRNAs present a mechanism by which genes with diverse functions on multiple pathways can be simultaneously regulated at the post-transcriptional level. However, little is known about the specific pathways through which miRNAs with specific sequence or structural motifs regulate the cellular processes. In this paper we showed the broad and deep characteristics of mature miRNAs according to their sequence and structural motifs. We investigated a distinct group of miRNAs characterized by the presence of specific sequence motifs, such as UGUGU, GU-repeats and purine/pyrimidine contents. Using computational function and pathway analysis of their targeted genes, we were able to observe the relevance of sequence and the type of targeted mRNAs. As the consequence of the sequence analysis we finally provide the comprehensive description of pathways, biological processes and proteins associated with the distinct group of characterized miRNAs. Here, we found that the specific group of miRNAs with UGUGU can activate the targets associated to the interferon induction pathway or pathways prominently observed during carcinogenesis. GU-rich miRNAs are prone to regulate mostly processes in neurogenesis, whereas purine/pyrimidine rich miRNAs could be involved rather in transport and/or degradation of RNAs. Additionally, we have also analyzed the simple sequence repeats (SSRs). Their variation within mature miRNAs might be critical for normal miRNA regular activity. Expansion or contraction of SSRs in mature miRNA might directly affect its mRNA interaction or even change the function of that distinct miRNA. Our results prove that due to the specific sequence features, these molecules can also be involved in well-defined cellular processes depending on their sequence contents. The pathway mapping and theoretical gene target identification allowed us to create a biological framework to show the relevance of the specific miRNAs in regulation the distinct type of targets.

Three hundred years of low non-paternity in a human population

When cuckoldry is frequent we can expect fathers to withhold investment in offspring that may not be theirs. Human paternal investment can be substantial and is in line with observations from tens of thousands of conceptions that suggest that cuckoldry is rare in humans. The generality of this claim seems to be in question as the rate of cuckoldry varies across populations and studies have mostly been on Western populations. Two additional factors complicate our conclusions, (1) current estimates of the rate of cuckoldry in humans may not reflect our past behaviour as adultery can be concealed by the use of contraceptives; and (2) it is difficult to obtain samples that are random with respect to their paternity certainty. Studies that combine genealogies with Y-chromosome haplotyping are able to circumvent some of these problems by probing into humans' historical behaviour. Here we use this approach to investigate 1273 conceptions over a period of 330 years in 23 families of the Afrikaner population in South Africa. We use haplotype frequency and diversity and coalescent simulations to show that the male population did not undergo a severe bottleneck and that paternity exclusion rates are high for this population. The rate of cuckoldry in this Western population was 0.9% (95% confidence interval 0.4-1.5%), and we argue that given the current data on historical populations we have to conclude that, at least for Western human populations, cuckoldry rate is probably in the range of 1%.

Curriculum and course materials for a forensic DNA biology course

The Forensic Science Education Programs Accreditation Commission (FEPAC) requires accredited programs offer a "coherent curriculum" to ensure each student gains a "thorough grounding of the natural…sciences." Part of this curriculum includes completion of a minimum of 15 semester-hours forensic science coursework, nine of which can involve a class in forensic DNA biology. Departments that have obtained or are pursuing FEPAC accreditation can meet this requirement by offering a stand-alone forensic DNA biology course; however, materials necessary to instruct students are often homegrown and not standardized; in addition, until recently, the community lacked commercially available books, lab manuals, and teaching materials, and many of the best pedagogical resources were scattered across various peer-reviewed journals. The curriculum discussed below is an attempt to synthesize this disparate information, and although certainly not the only acceptable methodology, the below discussion represents "a way" for synthesizing and aggregating this information into a cohesive, comprehensive whole.

Low historical rates of cuckoldry in a Western European human population traced by Y-chromosome and genealogical data

Recent evidence suggests that seeking out extra-pair paternity (EPP) can be a viable alternative reproductive strategy for both males and females in many pair-bonded species, including humans. Accurate data on EPP rates in humans, however, are scant and mostly restricted to extant populations. Here, we provide the first large-scale, unbiased genetic study of historical EPP rates in a Western European human population based on combining Y-chromosomal data to infer genetic patrilineages with genealogical and surname data, which reflect known historical presumed paternity. Using two independent methods, we estimate that over the last few centuries, EPP rates in Flanders (Belgium) were only around 1–2% per generation. This figure is substantially lower than the 8–30% per generation reported in some behavioural studies on historical EPP rates, but comparable with the rates reported by other genetic studies of contemporary Western European populations. These results suggest that human EPP rates have not changed substantially during the last 400 years in Flanders and imply that legal genealogies rarely differ from the biological ones. This result has significant implications for a diverse set of fields, including human population genetics, historical demography, forensic science and human sociobiology.

Multiplex genotyping assays for fine-resolution subtyping of the major human Y-chromosome haplogroups E, G, I, J, and R in anthropological, genealogical, and forensic investigations

Inherited DNA polymorphisms located within the nonrecombing portion of the human Y chromosome provide a powerful means of tracking the patrilineal ancestry of male individuals. Recently, we introduced an efficient genotyping method for the detection of the basal Y-chromosome haplogroups A to T, as well as an additional method for the dissection of haplogroup O into its sublineages. To further extend the use of the Y chromosome as an evolutionary marker, we here introduce a set of genotyping assays for fine-resolution subtyping of haplogroups E, G, I, J, and R, which make up the bulk of Western Eurasian and African Y chromosomes. The marker selection includes a total of 107 carefully selected bi-allelic polymorphisms that were divided into eight hierarchically organized multiplex assays (two for haplogroup E, one for I, one for J, one for G, and three for R) based on the single-base primer extension (SNaPshot) technology. Not only does our method allow for enhanced Y-chromosome lineage discrimination, the more restricted geographic distribution of the subhaplogroups covered also enables more fine-scaled estimations of patrilineal bio-geographic origin. Supplementing our previous method for basal Y-haplogroup detection, the currently introduced assays are thus expected to be of major relevance for future DNA studies targeting male-specific ancestry for forensic, anthropological, and genealogical purposes.

Appel Botha: The abc of a three hundred year old divorce case

In 1683 Maria Kickers and Jan Cornelitz got married in Cape Town. Today, 330 years later, the living patrilineal descendants of Maria's four sons, number in excess of 76,000 people. Curiously, none of them carry the surname Cornelitz - in fact, they are all called Botha and include former President P.W. Botha, general Louis Botha and Minister Pik Botha. The reason for this anomaly is also the reason why Jan got divorced from Maria in 1700. According to Maria's testimonies she did indeed have a long term relationship with Frederik Botha, but in her defence she claimed that her husband was impotent and that he actually encouraged her. Other witnesses, presumably prompted by Jan, gave testimonies that implied that Maria was in fact licentious. We combined haplotyping with the AmpFℓSTR(®) Yfiler™ kit with deep-rooting genealogies to show that Maria's first son was actually fathered by Ferdinandus Appel and that roughly half the living Bothas (38,000 people) actually descend from Ferdinandus Appel while the remaining three sons all stem from the same father, presumably Frederik Botha, and this implies that Maria's husband did not father any of her sons.

A comparison of Y-chromosomal lineage dating using either resequencing or Y-SNP plus Y-STR genotyping

We have compared phylogenies and time estimates for Y-chromosomal lineages based on resequencing ∼9 Mb of DNA and applying the program GENETREE to similar analyses based on the more standard approach of genotyping 26 Y-SNPs plus 21 Y-STRs and applying the programs NETWORK and BATWING. We find that deep phylogenetic structure is not adequately reconstructed after Y-SNP plus Y-STR genotyping, and that times estimated using observed Y-STR mutation rates are several-fold too recent. In contrast, an evolutionary mutation rate gives times that are more similar to the resequencing data. In principle, systematic comparisons of this kind can in future studies be used to identify the combinations of Y-SNP and Y-STR markers, and time estimation methodologies, that correspond best to resequencing data.

Genetic genealogy comes of age: perspectives on the use of deep-rooted pedigrees in human population genetics

In this article, we promote the implementation of extensive genealogical data in population genetic studies. Genealogical records can provide valuable information on the origin of DNA donors in a population genetic study, going beyond the commonly collected data such as residence, birthplace, language, and self-reported ethnicity. Recent studies demonstrated that extended genealogical data added to surname analysis can be crucial to detect signals of (past) population stratification and to interpret the population structure in a more objective manner. Moreover, when in-depth pedigree data are combined with haploid markers, it is even possible to disentangle signals of temporal differentiation within a population genetic structure during the last centuries. Obtaining genealogical data for all DNA donors in a population genetic study is a labor-intensive task but the vastly growing (genetic) genealogical databases, due to the broad interest of the public, are making this job more time-efficient if there is a guarantee for sufficient data quality. At the end, we discuss the advantages and pitfalls of using genealogy within sampling campaigns and we provide guidelines for future population genetic studies.

Genomics and genetics of human and primate y chromosomes

In mammals, the Y chromosome plays the pivotal role in male sex determination and is essential for normal sperm production. Yet only three Y chromosomes have been completely sequenced to date--those of human, chimpanzee, and rhesus macaque. While Y chromosomes are notoriously difficult to sequence owing to their highly repetitive genomic landscapes, these dedicated sequencing efforts have generated tremendous yields in medical, biological, and evolutionary insight. Knowledge of the complex structural organization of the human Y chromosome and a complete catalog of its gene content have provided a deeper understanding of the mechanisms that generate disease-causing mutations and large-scale rearrangements. Variation among human Y-chromosome sequences has been an invaluable tool for understanding relationships among human populations. Comprehensive comparisons of the human Y-chromosome sequence with those of other primates have illuminated aspects of Y-chromosome evolutionary dynamics over much longer timescales (>25 million years compared with 100,000 years). The future sequencing of additional Y chromosomes will provide a basis for a more comprehensive understanding of the evolution of Y chromosomes and their roles in reproductive biology.

A calibrated human Y-chromosomal phylogeny based on resequencing

We have identified variants present in high-coverage complete sequences of 36 diverse human Y chromosomes from Africa, Europe, South Asia, East Asia, and the Americas, representing eight major haplogroups. After restricting our analysis to 8.97 Mb of the unique male-specific Y sequence, we identified 6662 high-confidence variants, including single-nucleotide polymorphisms (SNPs), multi-nucleotide polymorphisms (MNPs), and indels. We constructed phylogenetic trees using these variants, or subsets of them, and recapitulated the known structure of the tree. Assuming a male mutation rate of 1 × 10⁻⁹ per base pair per year, the time depth of the tree (haplogroups A3-R) was ∼101,000–115,000 yr, and the lineages found outside Africa dated to 57,000–74,000 yr, both as expected. In addition, we dated a striking Paleolithic male lineage expansion to 41,000–52,000 yr ago and the node representing the major European Y lineage, R1b, to 4000–13,000 yr ago, supporting a Neolithic origin for these modern European Y chromosomes. In all, we provide a nearly 10-fold increase in the number of Y markers with phylogenetic information, and novel historical insights derived from placing them on a calibrated phylogenetic tree.

Forensic DNA testing

Forensic DNA testing has a number of applications, including parentage testing, identifying human remains from natural or man-made disasters or terrorist attacks, and solving crimes. This article provides background information followed by an overview of the process of forensic DNA testing, including sample collection, DNA extraction, PCR amplification, short tandem repeat (STR) allele separation and sizing, typing and profile interpretation, statistical analysis, and quality assurance. The article concludes with discussions of possible problems with the data and other forensic DNA testing techniques.

LENGTH DISTRIBUTIONS OF SIMPLE TANDEM REPEATS IN GENOMES

The length distributions of simple tandem repeats in the genomes of several organisms are evaluated and found to exhibit long-range correlations in A and T nucleotide bases related repeats for most eukaryotes. In particular, the length distributions of the mononucleotide A/T repeat units have longer tails than those of the C/G repeat units. Also, the length distributions of the dinucleotide repeat unit CG show a simple monotonously fast decreasing behavior, while those of repeat units AT, AG and AC have complicated structures at larger repeat lengths, especially for human, mouse and rat chromosomes. These distributive behaviors are due to the CpG deficiency in different genomes with different methylation activities. Especially, methyltransferases in vertebrates appear to methylate specifically the cytosine in CpG dinucleotides, and the methylated cytosines is prone to mutate to thymine by spontaneous deamination. The dinucleotide CpG would gradually decay into TpG and CpA. In addition, there is a peak in the distributions of repeat unit A at repeat-repeat separation 153 nt for humans and chimpanzees. We show that the long-tail behavior of mononucleotide repeat unit A and the peak at repeat separation 153 nt are due to the interspersed repetitive DNA sequences in humans and chimpanzees.

Evaluation of different sources of DNA for use in genome wide studies and forensic application

In the field of epidemiology, Genome-Wide Association Studies (GWAS) are commonly used to identify genetic predispositions of many human diseases. Large repositories housing biological specimens for clinical and genetic investigations have been established to store material and data for these studies. The logistics of specimen collection and sample storage can be onerous, and new strategies have to be explored. This study examines three different DNA sources (namely, degraded genomic DNA, amplified degraded genomic DNA and amplified extracted DNA from FTA card) for GWAS using the Illumina platform. No significant difference in call rate was detected between amplified degraded genomic DNA extracted from whole blood and amplified DNA retrieved from FTA™ cards. However, using unamplified-degraded genomic DNA reduced the call rate to a mean of 42.6% compared to amplified DNA extracted from FTA card (mean of 96.6%). This study establishes the utility of FTA™ cards as a viable storage matrix for cells from which DNA can be extracted to perform GWAS analysis.

WAMI: a web server for the analysis of minisatellite maps

Background

Minisatellites are genomic loci composed of tandem arrays of short repetitive DNA segments. A minisatellite map is a sequence of symbols that represents the tandem repeat array such that the set of symbols is in one-to-one correspondence with the set of distinct repeats. Due to variations in repeat type and organization as well as copy number, the minisatellite maps have been widely used in forensic and population studies. In either domain, researchers need to compare the set of maps to each other, to build phylogenetic trees, to spot structural variations, and to study duplication dynamics. Efficient algorithms for these tasks are required to carry them out reliably and in reasonable time.

Results

In this paper we present WAMI, a web-server for the analysis of minisatellite maps. It performs the above mentioned computational tasks using efficient algorithms that take the model of map evolution into account. The WAMI interface is easy to use and the results of each analysis task are visualized.

Conclusions

To the best of our knowledge, WAMI is the first server providing all these computational facilities to the minisatellite community. The WAMI web-interface and the source code of the underlying programs are available at http://www.nubios.nileu.edu.eg/tools/wami.

Inferring genetic ancestry: opportunities, challenges, and implications

Increasing public interest in direct-to-consumer (DTC) genetic ancestry testing has been accompanied by growing concern about issues ranging from the personal and societal implications of the testing to the scientific validity of ancestry inference. The very concept of "ancestry" is subject to misunderstanding in both the general and scientific communities. What do we mean by ancestry? How exactly is ancestry measured? How far back can such ancestry be defined and by which genetic tools? How do we validate inferences about ancestry in genetic research? What are the data that demonstrate our ability to do this correctly? What can we say and what can we not say from our research findings and the test results that we generate? This white paper from the American Society of Human Genetics (ASHG) Ancestry and Ancestry Testing Task Force builds upon the 2008 ASHG Ancestry Testing Summary Statement in providing a more in-depth analysis of key scientific and non-scientific aspects of genetic ancestry inference in academia and industry. It culminates with recommendations for advancing the current debate and facilitating the development of scientifically based, ethically sound, and socially attentive guidelines concerning the use of these continually evolving technologies.

Comprehensive analysis of simple sequence repeats in pre-miRNAs

Simple sequence repeats (SSRs) are tandem repeat units of 1-6 bp that are identified in various complete sequences. However, the distribution, nature, and origination of SSRs in pre-miRNAs, which are characteristic stem-loop sequences and are finally processed into ∼22 nt functional miRNAs contributing to regulate several biological processes, are still not well studied. The availability of large numbers of pre-miRNAs makes it possible to analyze and compare the occurrences of SSRs, the relative count of SSRs, or the longest SSRs in pre-miRNAs. In this study, we analyzed SSRs in 8,619 pre-miRNAs from 87 species, including Arthropoda, Nematoda, Platyhelminthes, Urochordata, Vertebrata, Mycetozoa, Protistae, Viridiplantae, and Viruses. We find that SSRs widely exist in the pre-miRNAs analyzed. Our analysis shows that mononucleotide repeats are the most abundant repeats, followed by dinucleotide repeats, whereas tri-, tetra-, penta-, and hexanucleotide repeats rarely occurred in pre-miRNAs. The number of SSRs per pre-miRNA on average ranges from 4.1 for viruses to 13.5 for Mycetozoa. Our results confirm that the number of repeats correlates inversely to the length of repeats. Generally, in each taxonomic group, the occurrence and relative count of SSRs decrease with the increase of repeat unit. SSRs do not exhibit obvious preference for special location in pre-miRNAs. The repeats in pre-miRNAs are complementary to repeats in coding or noncoding regions of genomes, and no significant difference is observed between these two classes with respect to the occurrence of repeats. These data on SSRs may become a useful resource of pre-miRNAs, and their possible functions are discussed.

Sequence determinants of human microsatellite variability

BACKGROUND

Microsatellite loci are frequently used in genomic studies of DNA sequence repeats and in population studies of genetic variability. To investigate the effect of sequence properties of microsatellites on their level of variability we have analyzed genotypes at 627 microsatellite loci in 1,048 worldwide individuals from the HGDP-CEPH cell line panel together with the DNA sequences of these microsatellites in the human RefSeq database.

RESULTS

Calibrating PCR fragment lengths in individual genotypes by using the RefSeq sequence enabled us to infer repeat number in the HGDP-CEPH dataset and to calculate the mean number of repeats (as opposed to the mean PCR fragment length), under the assumption that differences in PCR fragment length reflect differences in the numbers of repeats in the embedded repeat sequences. We find the mean and maximum numbers of repeats across individuals to be positively correlated with heterozygosity. The size and composition of the repeat unit of a microsatellite are also important factors in predicting heterozygosity, with tetra-nucleotide repeat units high in G/C content leading to higher heterozygosity. Finally, we find that microsatellites containing more separate sets of repeated motifs generally have higher heterozygosity.

CONCLUSIONS

These results suggest that sequence properties of microsatellites have a significant impact in determining the features of human microsatellite variability.

The hare and the tortoise: one small step for four SNPs, one giant leap for SNP-kind

A recently published study has used next-gen sequencing technology to resequence two Y chromosomes separated by 13 generations and discovered four single-base differences in approximately 10Mb DNA, suggesting that the Y chromosome euchromatin accumulates around one mutation per generation. Y-SNPs therefore now offer the best resolution of Y haplotypes and promise to distinguish almost every Y chromosome. This work illustrates the promise of current sequencing technology for forensically relevant applications.

Y chromosome variation in Europe: Continental and local processes in the formation of the extant gene pool

The polymorphism of the male-specific portion of the Y chromosome has been increasingly used to describe the composition of the European gene pool and to reconstruct its formation. Here the theoretical grounds and the limitations of this approach are presented, together with the different views on debated issues. The emerging picture for the composition of the male gene pool of the continent is illustrated, but local peculiarities that represent departures from the main trends are also highlighted, in order to illustrate the main unifying feature, i.e. the overlay of recent patterns onto more ancient ones. A synopsis of the main findings and conclusions obtained in regional studies has also been compiled.

Identification of distant family relationships

MOTIVATION

Family relationships can be estimated from DNA marker data. Applications arise in a large number of areas including evolution and conservation research, genealogical research in human, plant and animal populations, forensic problems and genetic mapping via linkage and association analyses. Traditionally, likelihood-based approaches to relationship estimation have used unlinked genetic markers. Due to the fact that some relationships cannot be distinguished from data at unlinked markers, and given the limited number of such markers available, there are considerable constraints on the type of identification problem that can be satisfactorily addressed with such approaches. The aim of this article is to explore the potential of linked autosomal single nucleotide polymorphism markers in this context. Throughout, we will view the problem of relationship estimation as one of pedigree identification rather than identity-by-descent, and thus focus on applications where determination of the exact relationship is important.

RESULTS

We show that the increase in information obtained by exploiting large sets of linked markers substantially increases the number of problems that can be solved. Results are presented based on simulations as well as on real data.

AVAILABILITY

The R library FEST is freely available from http://folk.uio.no/thoree/FEST.

Founders, drift, and infidelity: the relationship between Y chromosome diversity and patrilineal surnames

Most heritable surnames, like Y chromosomes, are passed from father to son. These unique cultural markers of coancestry might therefore have a genetic correlate in shared Y chromosome types among men sharing surnames, although the link could be affected by mutation, multiple foundation for names, nonpaternity, and genetic drift. Here, we demonstrate through an analysis of 1,678 Y-chromosomal haplotypes within 40 British surnames a remarkably high degree of coancestry that generally increases as surnames become rarer. On average, the proportion of haplotypes lying within descent clusters is 62% but ranges from 0% to 87%. The shallow time depth of many descent clusters within names, the lack of a detectable effect of surname derivation on diversity, and simulations of surname descent suggest that genetic drift through variation in reproductive success is important in structuring haplotype diversity. Modern patterns therefore provide little reliable information about the original founders of surnames some 700 years ago. A comparative analysis of published data on Y diversity within Irish surnames demonstrates a relative lack of surname frequency dependence of coancestry, a difference probably mediated through distinct Irish and British demographic histories including even more marked genetic drift in Ireland.

Comparative genomics and molecular dynamics of DNA repeats in eukaryotes

Repeated elements can be widely abundant in eukaryotic genomes, composing more than 50% of the human genome, for example. It is possible to classify repeated sequences into two large families, "tandem repeats" and "dispersed repeats." Each of these two families can be itself divided into subfamilies. Dispersed repeats contain transposons, tRNA genes, and gene paralogues, whereas tandem repeats contain gene tandems, ribosomal DNA repeat arrays, and satellite DNA, itself subdivided into satellites, minisatellites, and microsatellites. Remarkably, the molecular mechanisms that create and propagate dispersed and tandem repeats are specific to each class and usually do not overlap. In the present review, we have chosen in the first section to describe the nature and distribution of dispersed and tandem repeats in eukaryotic genomes in the light of complete (or nearly complete) available genome sequences. In the second part, we focus on the molecular mechanisms responsible for the fast evolution of two specific classes of tandem repeats: minisatellites and microsatellites. Given that a growing number of human neurological disorders involve the expansion of a particular class of microsatellites, called trinucleotide repeats, a large part of the recent experimental work on microsatellites has focused on these particular repeats, and thus we also review the current knowledge in this area. Finally, we propose a unified definition for mini- and microsatellites that takes into account their biological properties and try to point out new directions that should be explored in a near future on our road to understanding the genetics of repeated sequences.

Thomas Jefferson's Y chromosome belongs to a rare European lineage

We have characterized the Y chromosome carried by President Thomas Jefferson, the general rarity of which supported the idea that he, or a patrilineal relative, fathered the last son of his slave Sally Hemings. It belongs to haplogroup K2, a lineage representing only approximately 1% of chromosomes worldwide, and most common in East Africa and the Middle East. Phylogenetic network analysis of its Y-STR (short tandem repeat) haplotype shows that it is most closely related to an Egyptian K2 haplotype, but the presence of scattered and diverse European haplotypes within the network is nonetheless consistent with Jefferson's patrilineage belonging to an ancient and rare indigenous European type. This is supported by the observation that two of 85 unrelated British men sharing the surname Jefferson also share the President's Y-STR haplotype within haplogroup K2. Our findings represent a cautionary tale in showing the difficulty of assigning individual ancestry based on a Y-chromosome haplotype, particularly for rare lineages where population data are scarce.