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Mooney JA, Agranat-Tamir L, Pritchard JK, Rosenberg NA. On the number of genealogical ancestors tracing to the source groups of an admixed population. Genetics 2023; 224:iyad079. [PMID: 37410594 DOI: 10.1093/genetics/iyad079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 04/05/2023] [Indexed: 07/08/2023] Open
Abstract
Members of genetically admixed populations possess ancestry from multiple source groups, and studies of human genetic admixture frequently estimate ancestry components corresponding to fractions of individual genomes that trace to specific ancestral populations. However, the same numerical ancestry fraction can represent a wide array of admixture scenarios within an individual's genealogy. Using a mechanistic model of admixture, we consider admixture genealogically: how many ancestors from the source populations does the admixture represent? We consider African-Americans, for whom continent-level estimates produce a 75-85% value for African ancestry on average and 15-25% for European ancestry. Genetic studies together with key features of African-American demographic history suggest ranges for parameters of a simple three-epoch model. Considering parameter sets compatible with estimates of current ancestry levels, we infer that if all genealogical lines of a random African-American born during 1960-1965 are traced back until they reach members of source populations, the mean over parameter sets of the expected number of genealogical lines terminating with African individuals is 314 (interquartile range 240-376), and the mean of the expected number terminating in Europeans is 51 (interquartile range 32-69). Across discrete generations, the peak number of African genealogical ancestors occurs in birth cohorts from the early 1700s, and the probability exceeds 50% that at least one European ancestor was born more recently than 1835. Our genealogical perspective can contribute to further understanding the admixture processes that underlie admixed populations. For African-Americans, the results provide insight both on how many of the ancestors of a typical African-American might have been forcibly displaced in the Transatlantic Slave Trade and on how many separate European admixture events might exist in a typical African-American genealogy.
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Affiliation(s)
- Jazlyn A Mooney
- Department of Biology, Stanford University, Stanford, CA 94305, USA
- Department of Quantitative and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA
| | | | - Jonathan K Pritchard
- Department of Biology, Stanford University, Stanford, CA 94305, USA
- Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Noah A Rosenberg
- Department of Biology, Stanford University, Stanford, CA 94305, USA
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Rogalla-Ładniak U. The overview of forensic genetic genealogy. ARCHIVES OF FORENSIC MEDICINE AND CRIMINOLOGY 2022; 72:211-222. [PMID: 37405841 DOI: 10.4467/16891716amsik.22.023.17623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/06/2023] Open
Abstract
Forensic genetic genealogy (FGG) benefits largely from popularity of genealogical research within (mostly) American society and the advent of new sequencing techniques that allow typing of challenging forensic samples. It is considered a true breakthrough for both active and especially cold cases where all other resources and methods have failed during investigation. Despite media coverage generally highlighting its powers, the method itself is considered very laborious and the investigation may easily got suspended at every stage due to many factors including no hits in the database or breaks in traceable lineages within the family tree. This review summarizes the scope of FGG use, mentions most concerns and misconceptions associated with the technique and points to the plausible solutions already suggested. It also brings together current guidelines and regulations intended to be followed by law enforcement authorities wishing to utilize genetic genealogy research.
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Affiliation(s)
- Urszula Rogalla-Ładniak
- Faculty of Medicine, Ludwik Rydygier Collegium Medicum in Bydgoszcz; Nicolaus Copernicus University in Toruń, Poland
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de Vries JH, Kling D, Vidaki A, Arp P, Kalamara V, Verbiest MMPJ, Piniewska-Róg D, Parsons TJ, Uitterlinden AG, Kayser M. Impact of SNP microarray analysis of compromised DNA on kinship classification success in the context of investigative genetic genealogy. Forensic Sci Int Genet 2021; 56:102625. [PMID: 34753062 DOI: 10.1016/j.fsigen.2021.102625] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 10/25/2021] [Accepted: 10/27/2021] [Indexed: 11/04/2022]
Abstract
Single nucleotide polymorphism (SNP) data generated with microarray technologies have been used to solve murder cases via investigative leads obtained from identifying relatives of the unknown perpetrator included in accessible genomic databases, an approach referred to as investigative genetic genealogy (IGG). However, SNP microarrays were developed for relatively high input DNA quantity and quality, while DNA typically obtainable from crime scene stains is of low DNA quantity and quality, and SNP microarray data obtained from compromised DNA are largely missing. By applying the Illumina Global Screening Array (GSA) to 264 DNA samples with systematically altered quantity and quality, we empirically tested the impact of SNP microarray analysis of compromised DNA on kinship classification success, as relevant in IGG. Reference data from manufacturer-recommended input DNA quality and quantity were used to estimate genotype accuracy in the compromised DNA samples and for simulating data of different degree relatives. Although stepwise decrease of input DNA amount from 200 ng to 6.25 pg led to decreased SNP call rates and increased genotyping errors, kinship classification success did not decrease down to 250 pg for siblings and 1st cousins, 1 ng for 2nd cousins, while at 25 pg and below kinship classification success was zero. Stepwise decrease of input DNA quality via increased DNA fragmentation resulted in the decrease of genotyping accuracy as well as kinship classification success, which went down to zero at the average DNA fragment size of 150 base pairs. Combining decreased DNA quantity and quality in mock casework and skeletal samples further highlighted possibilities and limitations. Overall, GSA analysis achieved maximal kinship classification success from 800 to 200 times lower input DNA quantities than manufacturer-recommended, although DNA quality plays a key role too, while compromised DNA produced false negative kinship classifications rather than false positive ones.
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Affiliation(s)
- Jard H de Vries
- Erasmus MC, University Medical Center Rotterdam, Department of Internal Medicine, Dr. Molewaterplein 40, 3015 GD Rotterdam, the Netherlands
| | - Daniel Kling
- Department of Forensic Genetics and Toxicology, National Board of Forensic Medicine, Artillerigatan 12, 587 58 Linköping, Sweden
| | - Athina Vidaki
- Erasmus MC, University Medical Center Rotterdam, Department of Genetic Identification, Dr. Molewaterplein 40, 3015 GD Rotterdam, the Netherlands
| | - Pascal Arp
- Erasmus MC, University Medical Center Rotterdam, Department of Internal Medicine, Dr. Molewaterplein 40, 3015 GD Rotterdam, the Netherlands
| | - Vivian Kalamara
- Erasmus MC, University Medical Center Rotterdam, Department of Genetic Identification, Dr. Molewaterplein 40, 3015 GD Rotterdam, the Netherlands
| | - Michael M P J Verbiest
- Erasmus MC, University Medical Center Rotterdam, Department of Internal Medicine, Dr. Molewaterplein 40, 3015 GD Rotterdam, the Netherlands
| | - Danuta Piniewska-Róg
- Malopolska Centre of Biotechnology, Jagiellonian University, 30-387 Krakow, Poland; Department of Forensic Medicine, Jagiellonian University Medical College, 31-531 Krakow, Poland
| | - Thomas J Parsons
- International Commission on Missing Persons, Koninginnegracht 12a, 2514 AA Den Haag, the Netherlands
| | - André G Uitterlinden
- Erasmus MC, University Medical Center Rotterdam, Department of Internal Medicine, Dr. Molewaterplein 40, 3015 GD Rotterdam, the Netherlands; Erasmus MC, University Medical Center Rotterdam, Department of Epidemiology, Dr. Molewaterplein 40, 3015 GD Rotterdam, the Netherlands
| | - Manfred Kayser
- Erasmus MC, University Medical Center Rotterdam, Department of Genetic Identification, Dr. Molewaterplein 40, 3015 GD Rotterdam, the Netherlands.
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Kling D, Phillips C, Kennett D, Tillmar A. Investigative genetic genealogy: Current methods, knowledge and practice. Forensic Sci Int Genet 2021; 52:102474. [PMID: 33592389 DOI: 10.1016/j.fsigen.2021.102474] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 01/12/2021] [Accepted: 01/27/2021] [Indexed: 12/15/2022]
Abstract
Investigative genetic genealogy (IGG) has emerged as a new, rapidly growing field of forensic science. We describe the process whereby dense SNP data, commonly comprising more than half a million markers, are employed to infer distant relationships. By distant we refer to degrees of relatedness exceeding that of first cousins. We review how methods of relationship matching and SNP analysis on an enlarged scale are used in a forensic setting to identify a suspect in a criminal investigation or a missing person. There is currently a strong need in forensic genetics not only to understand the underlying models to infer relatedness but also to fully explore the DNA technologies and data used in IGG. This review brings together many of the topics and examines their effectiveness and operational limits, while suggesting future directions for their forensic validation. We further investigated the methods used by the major direct-to-consumer (DTC) genetic ancestry testing companies as well as submitting a questionnaire where providers of forensic genetic genealogy summarized their operation/services. Although most of the DTC market, and genetic genealogy in general, has undisclosed, proprietary algorithms we review the current knowledge where information has been discussed and published more openly.
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Affiliation(s)
- Daniel Kling
- Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden; Department of Forensic Sciences, Oslo University Hospital, Oslo, Norway.
| | - Christopher Phillips
- Forensic Genetics Unit, Institute of Forensic Sciences, University of Santiago de Compostela, Santiago de Compostela, Spain.
| | - Debbie Kennett
- Research Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Andreas Tillmar
- Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden; Department of Biomedical and Clinical Sciences, Faculty of Medicine and Health Sciences, Linköping University, Linköping, Sweden
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Abstract
The year 2020 marks the 50th anniversary of Theoretical Population Biology. This special issue examines the past and continuing contributions of the journal. We identify some of the most important developments that have taken place in the pages of TPB, connecting them to current research and to the numerous forms of significance achieved by theory in population biology.
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