Genetic genealogy

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As genetic genealogy and DNA genealogy is the application of genetics to the genealogy called. It uses DNA analyzes of the human genome in order to be able to prove or at least assess the degree of relationship between individuals or their ancestry .

Overview of the genome and its inheritance

Scheme of the XY / XX system in humans. Humans have 46 chromosomes. In women, two of them are X chromosomes (left). Men, on the other hand, have an X and a Y chromosome (right). The egg cells of a woman have 23 chromosomes, including one X chromosome. Sperm cells also have 23 chromosomes, one of which is either an X or a Y chromosome. The sex of the child is determined by which of these two sex chromosomes brings the invading sperm cell.

The DNA resides in the cell , with the autosomal DNA , X-DNA and Y-DNA in the nucleus and the mtDNA in the mitochondria . The autosomal DNA is organized into 22 pairs of chromosomes . The 23rd pair are the sex chromosomes, two X chromosomes for women, one X chromosome (X-DNA) and one Y-chromosome (Y-DNA) for men .

The children inherit their autosomal DNA from both parents. The X-DNA is passed on from father to daughter and from mother to all children ( X-linked inheritance ). The Y-DNA is passed on from father to sons ( paternal Y-chromosomal inheritance ). The mtDNA is passed on from the mother to the children ( maternal mtDNA inheritance). While chromosome pairs of the parents recombine ("mix") to form autosomal DNA in children and to X-DNA in daughters , Y-DNA and mtDNA are passed on as copies.

Both recombination and copying of the DNA have a certain probability of causing mutations and other hereditary defects, the effects of which range from harmless to lethal, depending on their position in the genes . Mutations can also have positive effects (see "successful" point mutations / SNPs ) and thus make a decisive contribution to evolution .

DNA from any two people is 99.5% identical; the remaining differences are called genetic variation . For comparison: chimpanzees and humans share 98.8% of the DNA. The appearance of humans ( phenotype ) is influenced by the genotype , but also by acquired traits that cannot be inherited. Since most of the hereditary factors (genes) are duplicated ( diploid : once on each chromosome pair), it is crucial in terms of the expression of the characteristics whether one of the genes is dominant , recessive , codominant or intermediate . The genetic variation is not geographically uniform on earth and can therefore be used to roughly determine the regions in which a person's ancestors lived (see variation due to the history of descent ).

Comparison of population genetic markers

DNA / marker
type		 Size
base pairs (Mb)		 Usable
loci 		Accessible
haplotypes 		DNA ancestors 10 generations ago Mutations
per Mb and generation		 SNPs
approx.		 Rec rate
( cM / Mb)		 Diversity Genetic drift Age Eff.
Pop. 		Genes
 protein-coding
genes
Autosomal 3,057 (93.5%) Thousands No Max. 1024, effective approx. 120 (53 paternal, 67 maternal) Moderate (0.02) 9.350k 1.1 High (0.08%) Low 1,000,000 years 1 43,259 (94.9%) 18,416 (95.4%)
X-DNA 155 (4.7%) Hundreds Yes Man max. 89,
woman max. 144		 Low (0.015) 474k? 0.8 Moderate (0.04%) Moderate 750,000 years 3/4 1,846 (4.1%) 824 (4.3%)
Y-DNA 58 (1.8%) 1 Yes Man 1, woman 0 High (0.033) 177k? 0 Low (0.02%) High 142,000 years 1/4 454 (1%) 54 (0.3%)
mtDNA 0.017 (0.001%) 1 Yes 1 Very high (1-300) 50? 0 Very high (0.4%) High 200,000 years 1/4 37 (0.08%) 13 (0.07%)

History: genetic material and its analysis

Charles Darwin's first sketch of the Family Tree of Life in 1837

The basic rules of genetics in simple inheritance were 1,866 published. They were based on family tree analysis and supported Darwin's theory of evolution . In 1869 a substance coming from cell nuclei (DNA) was first observed and named nucleus. From this time on, the doctrine of the role of the cell nucleus and that an individual develops from a single nucleated cell through division ( mitosis ). The equivalence of maternal and paternal germ cells for inheritance in sexual reproduction was also accepted .

The chromosome theory of inheritance was introduced in 1885 and practically proven by 1919. In 1943 the nucleus (DNA) is clearly identified as the carrier of genetic information. The structure of DNA was described in 1953 . In 1966 the genetic code was deciphered. In 1975, DNA sequencing revolutionized the biological sciences and ushered in the era of genomics .

The polymerase chain reaction (PCR) simplified the investigation of DNA from 1986 onwards. At the same time, the genetic fingerprinting (DNA fingerprinting) was developed and used legally for the prosecution of criminal offenses. Since 1995, mechanized, low-cost investigation methods for parentage reports based on DNA have been used for legal reports. From this time on, science was able to use DNA analyzes on a broad basis in population genetics .

In 1997, the first is eukaryotic genome (a yeast) completely sequenced, 2003, the reference sequence of the human genome as a result of the Human Genome Project . z. For example, the 1997 Cohen hypothesis on the Y-DNA of Jewish priests and the 2001 book The Seven Daughters of Eve on the mtDNA of the European "primeval mothers" have contributed to considerable excitement, approval and criticism, and ultimately to the popularity of genetic genealogy.

Since around 1999, DNA analyzes have also been affordable for private individuals. In April 2000, Family Tree DNA offered the first genetic genealogy tests to the public. The methods initially available are now very much out of date and their results are partially outdated. From this time on, genealogical DNA projects were formed on the Internet, an early form of social networks, which for the first time tested and discussed theories on paternal (Y-DNA markers, surname projects) and maternal (mtDNA markers) kinship lines outside of scientific studies. These social networks, or some of their most dedicated members, are constantly discovering DNA markers and also contribute to the development of theories on prehistoric human development and history.

A milestone in the acceptance of genetic genealogy is the Genographic Project . The anthropological study based on mtDNA markers, which was started in 2005 by the US National Geographic Society and IBM in cooperation with the University of Arizona and Family Tree DNA, lives to a large extent from the participation of voluntary paying testers, and has significantly increased the awareness of genetic genealogy resulted in a wealth of publications. By April 2010, more than 350,000 participation kits had been sold. In 2006, the turnover of all genealogical DNA testing companies (including laboratories) was estimated at $ 60 million.

Genealogical DNA family trees and networks

Dominant Y-DNA haplogroups in Europe

The haplogroups Y-chromosome (Y-DNA) and mitochondrial DNA (mtDNA) are examined in genealogical DNA analyzes . One uses genetic markers in the haplogroups to determine the degree of relationship. Y-DNA is routed along the paternal line and mtDNA is routed along the maternal line.

Haplogroups Y-DNA (paternal)

Since, in addition to mtDNA, only the Y-DNA enables a clear ancestral line to be traced, Y-DNA was also researched early on to establish the paternal line. The Y-DNA haplogroups are differentiated using a system developed by the Y Chromosome Consortium , using the letters A to R, as well as numbers and lowercase letters.

The haplogroup R1a is particularly common in Europe, north-central Asia, and India. Particularly high concentrations can be detected in Europe in Poland, Russia and Northern Europe. In India the highest concentration was found in the Brahmin caste.

Evolution tree haplogroups Y-chromosomal DNA (Y-DNA)
Adam of the Y chromosome
A00 A0'1'2'3'4
A0 A1'2'3'4
A1 A2'3'4
A2'3 A4 = BCDEF
A2 A3 B. CT 
|
DE CF
D. E. C. F.
|
G IJK H  
| |
G1 G2  IJ K 
| |
I. J L. K (xLT) T
| | |
I1 I2 J1 J2 M. NO P S.
| |
| |
N O Q R.
|
R1 R2
|
R1a R1b

Haplogroups mtDNA (maternal)

Exemplary representation of the development of mtDNA haplogroups based on a population of 8 women within 5 generations

Since mtDNA has 100-10,000 copies per cell and has a simple structure compared to chromosome DNA in the cell nucleus, it was preferred for cost-effective analysis. In addition, the maternal line can be reconstructed using the DNA in the mitochondria.

When old remains of Homo sapiens are found , mtDNA is often the only source of genetic information due to the degeneration of the DNA markers in the cell nucleus.

Human geneticist Bryan Sykes claims that there are seven mitochondrial lineages for modern Europeans (however, others estimate this number to be 11 or 12). However, the number of mitochondrial lineages for the entire world population is considerably greater.

Geographical distribution of the mtDNA haplogroups (maternal)

  • Southern Europe: J, K
  • Northern Europe: H, T, U, V, X
  • Middle East: Y, N
  • Africa: L, L1, L2, L3, L3
  • Asia: A, B, C, D, E, F, G
  • America (Native): A, B, C, D, X
Evolution Tree Haplogroup Mitochondrial DNA (mtDNA)
mtDNA Eva
L0 L1 L2 L3   L4 L5 L6
  M. N  
CZ D. E. G Q   A. S.   R.   I. W. X Y
C. Z B. F. R0   pre-JT P  U
HV JT K
H V J T

Autosomal DNA and X-DNA (origin, relationship)

Autosomal structure in Europe based on a PCA from SNPs

Since autosomal DNA and X-DNA are recombined and thus DNA segments are randomly inherited from the ancestors, complex mutation analyzes are necessary in order to be able to draw genealogical conclusions. Companies that offer DNA testing for commercial purposes test around 700,000 autosomal SNPs. Nevertheless, they are available from a price of € 49.

Geographical origin or descent

In order to be able to analyze the composition of the genetic ancestry in relation to geographical groups (peoples, clans), a sufficient number of test persons is required, whose ancestors come from a well-defined area.

Depending on the type of analysis and the choice of the decisive components or "data clusters", different evaluations and displays are possible. Principal component analyzes (PCA) are mostly represented in diagrams with two dimensions (X / Y). The two most meaningful components of the analysis are usually selected for the subject data available.

In the case of multidimensional evaluations, the components are specified for each test person; mostly in percentage values. Maps with the dominant components can also be created from such evaluations.

Evaluations also allow the creation of family trees, which show the closeness of the relationship between different subjects or clusters. Especially with this form of representation, the choice of the decisive component (s) is decisive and even small changes to the evaluation constellation produce different results.

Comparison of DNA sections, relationship

Using matching DNA segments, statistical conclusions can be drawn about the relationship. The segments are mostly compared based on the SNP mutations. The longer the matching segment, the closer the relationship.

Below a certain length of the DNA segments, instead of matching by descent (Identical by Descent - IBD), the probability of matching by the state (Identical By State - IBS) occurs, which could have arisen by chance. The length of the segments is given in centimorgan (cM).

Areas of Correspondence by Descent from Family Relationships
Art Parents child Cousin Child cousin Cousin 2 ° Child cousin 2 ° Cousin 3 ° Child cousin 3 ° Cousin 4 ° or further away
cM of all common DNA segments 3539-3748 548-1034 248-638 101-378 43-191 43-150 11.5-99 5-50
Number of common DNA segments 23-29 17-32 12-23 10-18 4-12 2-6? 1-4 0-2

More than 30 million people have now taken a DNA test at one of the four companies (Ancestry, 23andme, MyHeritage, FTDNA), which, according to an estimate by Dr. Yaniv Erlich about 60% of white Americans are identifiable by at least one third cousin or closer in one of the databases. Companies like Parabon NanoLabs have taken advantage of this and offer their services to the American law enforcement authorities. Using a DNA sample from the crime scene, a profile of 850,000 SNPs is created there, which among other things allows predictions about the appearance of the perpetrator (DNA phenotyping). In addition, this profile is compatible with GEDmatch and FTDNA, so that relatives of the perpetrator can be searched for there. CeCe Moore, the leading DNA genealogist at Parabo, was able to match 110 DNA samples to the person they were looking for within two years. In addition to solving the predominantly "cold" criminal cases (cold cases), she also helped stop active serial rapists in this way. In May 2019, the innocence of a man who spent over 20 years in prison for a murder was proven in a case. At the same time, the right perpetrator was identified and arrested.

Genealogical DNA analysis

The chromosomes of a man who is karyotype is 46, XY.

With the help of mtDNA and Y-DNA, maternal or paternal relationship can also be proven within genealogical times. However, it cannot be ruled out that, for example, a brother of a great-grandfather is the actual Y-DNA ancestor. Within paternal lines, Y-DNA analyzes often cannot help over the challenges of illegitimate paternity.

Since the turn of the millennium there have been an increasing number of companies offering DNA tests for private individuals. In international use, these offers are called "DTC tests" (Direct to Consumer).

criticism

Some test providers sometimes aggressively advertise questionable findings and keep silent about the fact that a simple mtDNA or Y-DNA analysis does not allow any serious scientific statement about the predominant ancestry or relationship, which can only be determined fragmentarily even by the autosomal DNA. Only a few test providers publish findings and the basis of their evaluations in a scientifically verifiable form. Certificates of historical origin ("clans", "indigenous peoples", etc.) based on mtDNA or Y-DNA must therefore be viewed critically or clearly limited to the maternal and paternal line. Their family trees and possible history through comparison with archaeological DNA finds have not yet been adequately researched scientifically until early historical times, so that many statements are based on assumptions. mtDNA and Y-DNA also only carry a very small proportion of the total genetic information.

The descent of historical personalities from whom DNA was not analyzed ( Ötzi , Tutankhamun, etc.) cannot be clearly proven genetically, as the random mutation rate of the markers in Y-DNA and mtDNA does not allow a clear assignment of the generation, so only proximity the relationship in the haplogroup can be determined. In addition, the comparisons with historical DNA are often based on too few markers or unpublished findings.

The mass media also contribute their share of dubious exaggerated reports to sensation-hungry conclusions from DNA analyzes.

The criticism of medical health predictions based on DNA analyzes is even more pronounced, since the state of research is still rudimentary.

While the analysis of some common markers in mtDNA and Y-DNA is still relatively harmless, "private SNPs" already mark the relationship in this line. The analysis of autosomal DNA marks the test person and the closer relationship particularly comprehensively. 70 markers can be enough to identify a person. Therefore, when sending in DNA samples, storing, analyzing and saving the same by companies, as well as when publishing information, the consequences must be observed.

Possible abuse

The DNA analysis for genetic genealogy raises legal and ethical questions that have not yet been adequately clarified. In DNA tests, the question is often whether hereditary diseases can be detected in the test person's DNA. Accordingly, such commercial DNA tests are banned in France, for example. In the USA, 23andMe had to withdraw one of the tests already on the market on the instructions of the FDA ( Food and Drug Administration ) . In Germany, however, commercial DNA tests are allowed. In addition, humanities scholars raise the question of how the genealogical data in the archives that have been free to date and the genealogical knowledge gathered over decades in unpaid detailed work by amateur genealogists and professional researchers can be placed under the protection of UNESCO as intangible cultural heritage and preserved from appropriation by private companies can. The lack of data protection is also problematic : 23andMe is known to sell customer data to pharmaceutical companies. Ancestry shares the DNA results with Spotify .

In June 2019, Ancestry.com received the negative “ BigBrotherAward ” in Germany in the newly created biotechnology category , “because it encourages people interested in family research to send in their saliva samples. Ancestry sells the genetic data to commercial pharmaceutical research, enables covert paternity tests and creates the data basis for police genetic screening. ”In his laudation, lawyer Thilo Weichert drew the following conclusion:

“Nothing against genetic analysis. These can be an important source of knowledge for family research, but especially for medicine. But the samplers should be clear about what they are doing. Vendors like Ancestry misuse the interest in family research to amass a genome treasure for commercial research, because that's their real business model. The data protection rights of the sampler and their relatives must be respected. The German data protection and disclosure obligations are deliberately ignored by Ancestry out of profit interest. We see a trend here: After the exploitation of Internet data, the exploitation of genetic data is the next big thing. Ancestry is the top dog who knows no data protection or fundamental rights scruples. "

- Laudation from Thilo Weichert at the "Big Brother Awards 2019"

See also

literature

  • Mark A. Jobling, Chris Tyler-Smith: The Human Y Chromosome - An Evolutionary Marker Comes of Age . In: Nature 4/2003. Page 598–612.
  • Christian Zelger: Erbgut and Erbhof - About the possibilities of genetic genealogy . In: Schlern 4/2013. Edited by Irmgard Flies. Athesia Verlag 2013. Pages 66–78.
  • Timo Kracke: A trip into the DNA genealogy. In: genealogy. In the footsteps of the ancestors . Published by the Verein für Computergenealogie e. V. Bremen 2010. 84-87.
  • Hermann Metzke: Genealogy and human genetics. In: Paperback for family history research. Edited by Wolfgang Ribbe and Eckart Henning . Verlag Degener & Co, Insingen 2006, pages 98-110.
  • Tobias Schmidt: Genealogy by DNA. Perspectives for genealogists . In: Genealogy and DNA. Published by the Verein für Computergenealogie e. V. Münster 2003. Pages 8–11.
  • Tobias Kemper: Family history research plus natural science is DNA genealogy . In: Computergenealogie 32 (2017), Heft 2, pp. 26–31

Web links

Individual evidence

  1. ↑ a b c Vega Genome Browser 46: Homo sapiens (GRCh37.p5) ( English ) Wellcome Trust Sanger Institute. January 12, 2012. Retrieved March 4, 2012.
  2. ↑ International HapMap Project Overview ( English ) International HapMap Project. February 22, 2012. Retrieved March 5, 2012.
  3. ↑ Luke Jostins: How Many Ancestors Share Our DNA? ( English ) Genetic Inference Blog. November 11, 2009. Archived from the original on May 19, 2013. Retrieved March 7, 2012.
  4. ↑ Joseph Lachance, Benjamin Vernot, Clara C. Elbers, Bart Ferwerda, Alain Froment, Jean-Marie Bodo, Godfrey Lema, Wenqing Fu, Thomas B. Nyambo, Timothy R. Rebbeck, Kun Zhang, Joshua M. Akey, Sarah A. Tishkoff, Evolutionary History and Adaptation from High-Coverage Whole-Genome Sequences of Diverse African Hunter-Gatherers , Cell, Volume 150, Issue 3, 3 August 2012, Pages 457-469, ISSN  0092-8674 , doi : 10.1016 / j.cell .2012.07.009 .
  5. ↑ Felix v. Schroeder: About the inheritance of the X chromosome in the pedigree . In: The Herald (Berlin) . 9, No. 9, 1980, pp. 295-296. Retrieved March 7, 2012.
  6. ↑ Fulvio Cruciani, Beniamino Trombetta, Andrea Massaia, Giovanni Destro-Bisol, Daniele Sellitto, Rosaria Scozzari: A Revised Root for the Human Y Chromosomal Phylogenetic Tree: The Origin of Patrilineal Diversity in Africa . In: The American Journal of Human Genetics . 88, No. 6, June 2011, ISSN  0002-9297 , pp. 814-818. doi : 10.1016 / j.ajhg.2011.05.002 .
  7. ↑ Soares P, Ermini L, Thomson N, et al. : Correcting for purifying selection: an improved human mitochondrial molecular clock . In: Am. J. Hum. Genet. . 84, No. 6, June 2009, pp. 740-59. doi : 10.1016 / j.ajhg.2009.05.001 . PMID 19500773 . PMC 2694979 (free full text). University of Leeds - New 'molecular clock' aids dating of human migration history
  8. ↑ a b Mitochondrial DNA
  9. ^ Karl Skorecki, Sara Selig, Shraga Blazer et al .: Y chromosomes of Jewish priests. In: Nature . Volume 385, 1997, p. 32, doi: 10.1038 / 385032a0 , full text ( Memento from November 5, 2012 in the Internet Archive )
  10. ↑ http://edition.cnn.com/2005/TECH/science/04/12/genographic/index.html
  11. ^ The Genographic Project - Project News . National Geographic Society. 2011. Archived from the original on July 5, 2011. Retrieved March 5, 2012.
  12. ^ Blaine Bettinger: How Big Is the Genetic Genealogy Market? ( English ) The Genetic Genealogist. November 6, 2007. Retrieved March 5, 2012.
  13. ↑ Leah Larkin: Autosomal DNA Database Growth. Retrieved June 22, 2020 .
  14. ↑ Yaniv Erlich: Identity inference of genomic data using long-range familial searches. Retrieved June 22, 2020 .
  15. ↑ Parabon Nano Labs: Parabon Snapshot Advanced DNA analysis. Retrieved June 22, 2020 .
  16. ↑ KC Baker: Forensic DNA Expert CeCe Moore Solves Decades-Old Cold Cases in ABC's The Genetic Detective. Retrieved June 22, 2020 .
  17. ↑ Parabon NanoLabs: Published Police Investigations. Retrieved June 22, 2020 .
  18. ^ Eleonora Haas: CeCe Moore's trickiest cold case. Retrieved June 22, 2020 .
  19. ↑ Example: Julia Reichert: Correction: Ötzi was not a Sardinian . Science information service. February 29, 2012. Retrieved March 5, 2012.
  20. ↑ Bastian Greshake, Philipp Bayer: spack0-1: What the post-genomics era means for privacy . YouTube user lisphans. December 30, 2011. Retrieved March 5, 2012.
  21. ^ Frédéric Kaplan, Isabella di Lenardo: Family tree for sale . In: Le Monde diplomatique . WOZ the weekly newspaper, Zurich February 18, 2018, p. 2 .
  22. ^ John Herrman: Why Is This Happening: Content for Humans About the Content of Humans - Spotify and Ancestry team up for that saliva sample sound. In: New York Times. October 5, 2018, accessed June 21, 2019 .
  23. ↑ Big Brother Awards 2019: Homepage. Retrieved June 21, 2019.
  24. ^ Thilo Weichert : Laudation Biotechnik: Ancestry.com. In: bigbrotherawards.de. June 8, 2019, accessed June 21, 2019 .