A genealogy DNA test is a DNA-based test that looks at the specific location of a person's genome to determine ethnic relation and ancestral pedigree. The results provide information about the ethnic group of test subjects can be derived from and about other individuals who may be associated with it.
Three main types of genealogical DNA testing are available, with each looking at different parts of the genome and useful for different types of genealogy research: Autosomal, Mitochondria, and Y. In general, genealogical DNA testing does not provide information about medical conditions or disease
Video Genealogical DNA test
DNA testing for consumers
The first company to provide genetic DNA testing directly to consumers is the now-defunct GeneTree. However, it does not offer multi-generation genealogical tests. In the fall of 2001, GeneTree sold its assets to the Gensalogy of Sorenson Molecular Salt Lake City (SMGF) Foundation from 1999. While operating, SMGF gave free Y-Chromosome and mitochondrial DNA tests to thousands of people. Later, GeneTree returns to genetic testing for genealogy in conjunction with Sorenson's parent company and is ultimately part of the assets acquired in the purchase of Ancestry.com from SMGF.
In 2000, the Family Tree DNA, founded by Bennett Greenspan and Max Blankfeld, was the first company dedicated to direct-to-consumer testing for genealogy research. They initially offered eleven markers of STR Y-Chromosome test and HVR1 mitochondrial DNA test. They were initially tested in partnership with the University of Arizona.
In 2007, 23andMe was the first company to offer genuine direct-to-consumer genetic testing. It was also the first to apply using autosomal DNA for ancestor testing, used by all other large companies.
By 2018 it is estimated that more than 12 million people have tested their DNA for genealogical purposes, most of which are in the US.
Maps Genealogical DNA test
Procedures
Genealogical DNA tests were performed on DNA samples. This DNA sample can be obtained by stretching the cheeks (also known as buccal swabs), spit-cups, mouthwashes, and chewing gum. Typically, sample collections use home test kits provided by service providers such as 23andMe, AncestryDNA, Family Tree DNA, or MyHeritage. After following the kit instructions on how to collect samples, it is returned to the supplier for analysis.
Test type
There are three main types of genealogical DNA tests: Autosomal and X-DNA, Y-DNA and mtDNA. The
- Autosomal view chromosomes 1-22 and X. Autosomes (chromosomes 1-22) are inherited from both parents and all ancestors recently. The X-chromosome follows a special inheritance pattern. Ethnic estimates are often included with this kind of testing.
- Y-DNA sees the Y chromosome, which is passed down to a boy, and therefore can only be taken by men to explore their direct line of daddy.
- mtDNA sees mitochondria, inherited from mother to child and can be used to explore a person's straight line.
Y-DNA and mtDNA can not be used for ethnic estimates, but can be used to search for a person's haplogroup, which is not geographically distributed. Direct-to-consumer DNA testing companies are often labeled haplogroups by continents or ethnicities (eg, "African haplogroup" or "hoblogroup Viking"), but these labels may be speculative or misleading.
Autosomal DNA testing (atDNA)
What was tested
Autosomal DNA is present on 22 pairs of chromosomes that are not involved in determining one's sex. Autosomal DNA reunites each generation, and new offspring receive a set of chromosomes from each parent. It is inherited exactly the same from both parents and more or less the same from grandparents to about 3x great-grand parents. Therefore, the number of markers (one of two or more known variants in the genome in a particular location - known as single nucleotide polymorphism or SNP) derived from a particular ancestor decreases by about half each generation; that is, an individual receives half of their markers from every parent, about a quarter of their markers from each of the grandparents; about one-eighth of their markers from each great-grandfather, etc. Inheritance is more random and not the same from the more distant ancestors. Generally, genealogical DNA testing may test around 700,000 SNPs (specific points in the genome).
Reporting process
The preparation of reports on DNA in the sample takes place in several stages:
- identification of base pairs of DNA at certain SNP locations
- comparison with previously saved results
- game interpretation
Identify base pair
All major service providers use equipment with the chips provided by Illumina. The chip determines the location of the tested SNP. Different versions of chips are used by different service providers. In addition, the latest version of Illumina chips can test different sets of SNP locations. The list of SNP locations and base pairs in those locations is usually available to customers as "raw data". Raw data can sometimes be uploaded to another service provider to generate additional interpretations and matches. For additional analysis, data can also be uploaded to GEDmatch (a set of third-party web-based tools analyzing raw data from major service providers).
Match Identification
The main component of autosomal DNA testing is the matching of others. Where the individuals tested had the same number of SNPs as individuals previously tested in the company database, it can be concluded that they share a segment of DNA in their genome section. If the segment is longer than the number of thresholds set by the testing company, then these two individuals are considered as matches. Unlike base pair identification, the database used to test new samples, and the algorithms used to determine matches, are proprietary and specific to each company.
The unit for the DNA segment is centimorgan (cM). For comparison, the full human genome is about 6,500 cM. The shorter the length of the game, the more likely it is that the game is fake. An important statistic for subsequent interpretation is the length of the shared DNA (or the percentage of the shared genome).
Autosomal match interpretation
Most companies will show customers how many cM they share, and how many segments. From the number of cM and segments, the relationship between two individuals can be estimated, but due to the random nature of DNA inheritance, the approximate relationship, especially for distant relatives, is only approximate. Some distant cousins ​​will not fit at all. Although information about certain SNPs may be used for some purposes (eg showing the possibility of eye color), the key information is the percentage of DNA shared by 2 individuals. This can indicate the closeness of the relationship. However, it does not indicate the role of 2 individuals - eg 50% share suggests a parent-child relationship, but does not identify which individual is the parent.
Various techniques and advanced analysis can be done on this data. This includes features such as Common/Joint Matches, Chromosome Browsers, and Triangulations. This analysis is often necessary if DNA evidence is used to prove or dispute a particular relationship.
X-chromosome DNA testing
X-chromosome SNP results are often included in autosomal DNA testing. Both men and women receive an X chromosome from their mother, but only women receive a second X chromosome from their father. X-chromosomes have a special line of inheritance patterns and can be useful in narrowing the ancestral line significantly compared to atDNA - eg an X-chromosome match with men can only come from the maternal side. Like the autosomal DNA, X chromosome DNA undergoes random recombination in every generation (except for the father-to-child chromosome is unchanged). There is a special inheritance graph that illustrates the possible pattern of inheritance of X-chromosome DNA for both men and women.
STRs
Some genealogical companies offer an autosomal STR (short tandem repetition). This is similar to STR Y-DNA. The number of STRs offered is limited, and not genealogically helpful.
Law enforcement agencies in the US and UK use the data of an autosomal STR to identify criminals.
Mitochondrial DNA Testing (mtDNA)
Mitochondrion is a component of human cells, and it contains its own DNA. Mitochondrial DNA typically has 16,569 base pairs (the amount may vary slightly depending on the addition or removal mutation) and is much smaller than that of the human genome that has 3.2 billion base pairs. Mitochondrial DNA is transmitted from mother to child, so maternal ancestors can be directly traced using mtDNA. Transmission occurs with relatively rare mutations compared with genomic DNA. The perfect match found on other people's mtDNA tests shows the same forebears probably between 1 and 50 generations ago. Further matches to certain haplogroups or subclasses may be related to common geographic origin.
There is a debate over whether paternal mtDNA transmission may occur in humans. Some authors cite paternal mtDNA transmission as an invalid mtDNA test. However, other studies suggest that paternal mtDNA is never transmitted to offspring, which would validate the use of mTDNA testing for pedigrees.
What was tested
mtDNA, with the current convention, is divided into three regions. They are the coding region (00577-16023) and the two Region Hiper Variables (HVR1 [16024-16569], and HVR2 [00001-00576]).
The two most common mtDNA tests are the order of HVR1 and HVR2 and the full order of mitochondria. Generally, testing only HVR has a limited use of genealogies that is becoming increasingly popular and accessible to have the full order. The complete mtDNA sequence is offered only by Family Tree DNA among large and somewhat controversial testing companies because region coding DNA may reveal medical information about test takers
Haplogroups
All humans descend on the female line directly from Mitochondrial Eve, a woman who lived perhaps some 200,000 years ago in Africa. Different branches of the offspring are different haplogroups. Most mtDNA results include a prediction or assertion of a person's Haplogroup mtDNA. The mitochrondial haplogroup is greatly popularized by The Seven Daughters of Eve, which explores mitochondrial DNA.
Understanding mtDNA test results
It is not normal for the test results to provide a baseline list of results. In contrast, the results are usually compared with the Cambridge Reference Sequence (CRS), which is the first European mitochondrial mitochondria to be published in 1981 (and revised in 1999). The difference between a CRS and a tester is usually very small, making it easier than listing one's raw results for each base pair.
- Example
Note that in HVR1, instead of reporting the exact base pair, for example 16111, 16 is often removed for giving in this example 111. The letters refer to one of the four bases (A, T, G, C) that form human DNA.
mtDNA in the news
The mtDNA test is used by University of Leicester archaeologists to verify the remains of the King Richard III skeleton, which was discovered in September 2012.
Test Y chromosome (Y-DNA)
Y-Chromosome is one of the 23rd human chromosome pairs. Only men have Y chromosomes, because women have two X chromosomes in their 23rd pair. A patrilineal paternal ancestor, or an ancestral ancestor, can be traced using DNA on his Y-chromosome (Y-DNA), since the Y chromosome is transmitted from father to child virtually unchanged. The results of a man's test compared with other people's results to determine the time frame in which the two men share the most common ancestor, or MRCA, in their direct patrilineal line. If their test results are so close, they are related in a genealogically useful time frame. The clan project is where many people whose Y chromosome is a good collaborator to find their common ancestors.
Women who want to determine their father's DNA ancestor can directly ask their father, brother, father's uncle, father's grandfather, or father's uncle's son (their cousin) to take the test for them.
There are two types of DNA testing: STR and SNP.
STR marker
The most common is STR (short tandem repetition). Certain sections of DNA are examined for repetitive patterns (eg ATCG). How many times the repeat is the value of the marker. A typical test tests between 12 and 111 markers of STR. STR mutates quite frequently. The results of two individuals were then compared to see if there was a match. Close the game can join the family name project. The DNA companies will usually give an estimate of how closely related two people, in terms of generation or year, based on the difference between their results.
SNP and Haplogroup markers
A person's haplogroup can often be inferred from their STR results, but can be proven only by a Y-chromosome SNP test (Y-SNP test).
Single nucleotide polymorphism (SNP) is a change to a single nucleotide in DNA sequences. Typical SNP Y-DNA tests tested around 20,000 to 35,000 SNPs. Getting a SNP test allows a much higher resolution than STR. It can be used to provide additional information about the relationship between two individuals and to confirm the haplogroup.
All human humans descend on the father line from a man dubbed Adam Y-chromosome, which lived probably between 200,000 and 400,000 years ago. A 'family tree' can be drawn showing how a man today descends from him. A different branch of this tree is a different haplogroup. Most haplogroups can be subdivided several times into sub-clades. Some known sub-klades are established in the last 1000 years, which means their time span is approaching the genealogical era (about 1500 and beyond).
New sub-clades of haplogroup can be found when testing individuals, especially if they are non-European. The most significant of these new discoveries is in 2013 when the A00 haplogroup was discovered, which required the theory of Adam's Y chromosome to be significantly revised. Haplogroup was discovered when an African-American man tested STR on FamilyTreeDNA and the results were found to be unusual. The SNP test confirms that it does not patrilineally descend from the "old" Adam Y-chromosomal and becomes a much older man to Adam Y-Chromosomal.
Using DNA test results
Estimated Ethnicity
Many companies offer percentage details based on ethnicity or region. Generally the world is defined to be around 20-25 territories, and the approximate percentage of DNA inherited from each is expressed. This is usually done by comparing the frequencies of each Autosomal DNA marker that is tested in many population groups. The reliability of this type of test depends on the size of the comparison population, the number of markers tested, the informative value of the ancestors of the tested SNP, and the degree of mixing in the person tested. Previous ethnic forecasts are often very inaccurate, but the accuracy has improved greatly. Usually the results at the continental level are accurate, but more specific assertions of the test may turn out to be false. For example, Europeans often accept excessive Scandinavian proportions. Testing firms often regularly update their ethnic forecasts, altering individual ethnic forecasts.
Audience
Interest in genealogical DNA testing has been associated with an increased curiosity about traditional pedigree and to more common personal origins. Those who test traditional pedigrees often use a combination of autosomal, mitochondrial, and Y-Chromosome tests. Those with an interest in ethnic origin are more likely to use autosomal testing. However, answering specific questions about the ethnic origin of a particular lineage may be best suited for a mtDNA test or a Y-DNA test.
The mother's test
For the recent genealogy, exact matching in the complete sequence of mtDNA is used to confirm the common ancestor on the maternal line directly between two suspected siblings. Because mtDNA mutations are so rare, almost perfect pairs are usually not considered relevant to the last 1 to 16 generations. In cultures that do not have a matrilineal family name to be inherited, it is unlikely that the relative above has many generations of ancestors in their matrilineal information table as in the patrilineal or Y-DNA case above: for more information on this difficulty in traditional genealogy , due to lack of surname matrilineal (or matrinames), see Matriname. However, the testing foundation is still two alleged offspring of one person. These hypotheses and DNA pattern tests are similar to those used for autosomal DNA and Y-DNA.
Test for ethnicity and other group membership
As discussed above, autosomal tests usually report the proportion of individual ethnicity. This effort is to measure the inheritance of individual mixed geographies by identifying specific markers, called descendants of hereditary information or AIM, that are related to the population of a particular geographic area. Geneticist Adam Rutherford has written that these tests "do not always show your geographical origin in the past, they show with whom you have a common ancestor today."
Haplogroups determined by Y-DNA and mtDNA tests are often not geographically distributed. Many direct-to-consumer DNA tests illustrate this relationship to infer the ancestors of the people who took the test. Most tests describe haplogroups according to their most frequently attributed continents (eg, "European haplogroups"). When Leslie Emery and collaborators tested mtDNA haplogroup as a predictor of continental origin in individuals in the Human Genetic Diversity Panel (HGDP) dataset and 1000 Genomes (1KGP), they found that only 14 of the 23 haplogroups had a success rate above 50% HGDP samples, as well as "about half" of haplogroups at 1KGP. The authors conclude that, for most people, "mtDNA-haplogroup membership provides limited information about continental ancestors or regions of the original continent."
African ancestors
The Y-DNA test and the mtDNA may be able to determine with which people in Africa today somebody shares a direct line of part of their ancestors, but the patterns of historical migration and historical events obscure the traces of the ancestral group. Due to the long joint history in the US, about 30% of African American men have a European Y-Chromosome haplogroup About 58% of African Americans have at least the equivalent of one great-grandfather (13%) of European ancestors. Only about 5% have the equivalent of one great-grandmother of an American native ancestor. In the early nineteenth century, large families of Free Colored People had been established in the Chesapeake Bay region which was descended from free men during the colonial period; most of them have been documented as descendants of white men and African women (servants, slaves or free). Over time, various groups marry more in mixed, black or white community races.
According to authorities like Salas, nearly three-quarters of the African-American ancestors who were taken in slavery were from areas in West Africa. The African-American movement to discover and identify with ancestral tribes has evolved since DNA testing is available. African Americans usually can not easily track their ancestors during the years of slavery through the study of surnames, censuses and property records, and other traditional ways. Genealogical DNA testing may link to regional African heritage.
United States - melungeon Testing
Melungeons are one of many multiracial groups in the United States with myth-wrapped origins. Historical research by Paul Heinegg has documented that many Melungeon groups in the Upper South are from free mixed races in colonial Virginia and the union results between Europeans and Africans. They moved to the borders of Virginia, North Carolina, Kentucky, and Tennessee to gain freedom from racial barriers in the plantation area. Several attempts, including a number of ongoing studies, have examined the family's genetic make-up historically identified as Melungeon. Most of the results show mainly on the mixture of Europe and Africa, supported by historical documentation. Some may have a native American heritage as well. Although some companies provide additional Melungeon research material with Y-DNA and mtDNA tests, any test will allow comparison with recent and past Melungeon DNA study results.
native American ancestor
The pre-Columbian native people in the United States are called "Native Americans" in American English. Autosomal testing, Y-DNA, and mtDNA testing can be performed to determine the ancestors of Native Americans. A Mitochondrial Haplogoup mitigation test based on mutations in Hypervariable Areas 1 and 2 can determine whether the female direct line belongs to one of the Canadian American Native Haplogroups, A, B, C, D or X. Most Native Americans belong to one of five haplogroup identified mtDNA. Thus, being in one of the groups provided evidence of potential Genetic Americans. However, ethnic DNA results can not be used instead of legal documentation. Native American tribes have their own membership requirements, often based on at least one ancestor of a person who has been included in the census of the native Americans (or scrolls) of tribes prepared during the making of the treaty, relocation to reservation or land sharing at the end of the twentieth century. 19 and early 20th century. One such example is the Dawes Rolls.
ancestor Cohanim
The Cohanim (or Kohanim) is a line of patrilineal descendants in Judaism. According to the Bible, Cohanim's ancestor was Aaron, Moses' brother. Many believe that the offspring of Aaron can be verified by the Y-DNA test: the first study published in the Y-Chromosome genealogical DNA test found that a significant percentage of Cohens had similar DNA, more than the general population of Jews or the Middle East. This cohens tends to belong to Haplogroup J, with the Y-STR scores very close together around the haplotype known as Cohen Capital Haplotype (CMH). This can be consistent with the same common ancestor, or with the hereditary priesthood originally founded from members of a closely related clan.
However, the original study only tested six Y-STR markers, which were considered low-resolution tests. In response to the low resolution of the original CMH 6-marker, the FTDNA testing company released the more specific 12-mark CMH mark for the large Cohens group closely linked in Haplogroup J1.
A further academic study published in 2009 examined more STR markers and identified a sharper SNP haplogroup, J1e * (now J1c3, also called J-P58 *) for the J1 pedigree. The study found that 46.1% of Kohanim carry the Y chromosome belonging to a father lineage (J-P58 *) which probably originated in the Near East long before the spread of Jewish groups in the Diaspora Support for the Near East origin of this lineage came from high frequency in the sample we, the Bedouins, Yemen (67%) and Jordan (55%) and the drastic decrease in frequency as one moves away from Saudi Arabia and the Near East (Figure 4) are striking contrasts between the relatively high frequencies of J-58 * in the Jewish population (Ã, Â »20%) and Kohanim (Ã, 46%) and very low frequencies in samples of non-Jewish populations living in the Jewish diaspora communities outside of the Near East."
The last phylogenetic research for the J-M267 haplogroup puts the "Y-chromosome Aaron" in the subhaplogroup of J-L862, L147.1 (approximate age 5631-6778yBP YBP): YSC235 & gt; PF4847/CTS11741 & gt; YSC234 & gt; ZS241 & gt; ZS227 & gt; Z18271 (approximate age 2731yBP).
European Testing
For people with European ancestors, mtDNA tests are offered to determine which of the eight "genera" of European mothers who are the direct ancestors of the mother's front line. This mtDNA haplotype test was popularized in the book The Seven Daughters of Eve .
Benefits
The genealogical DNA test has become popular because of the ease of testing at home and its usefulness in completing genealogy research. Genealogical DNA tests allow a person to determine with high accuracy whether he or she is associated with another person within a certain period of time, or with the certainty that he or she is unrelated. DNA tests are considered to be more scientific, conclusive and quicker than searching for civilian records. However, they are limited by restrictions on the line that can be learned. Civil records are always just as accurate as those who have given or written information.
Y-DNA test results are usually expressed as probabilities: For example, under the same name, a perfect 37/37 marker assay provides 95% of the newest common ancestors (MRCA) within 8 generations, while 111 of 111 marker matches provide 95% the same possibilities from MRCA that are only in 5 generations back.
As presented above in mtDNA testing, if a perfect match is found, mtDNA test results may be helpful. In some cases, research according to traditional genealogical methods is difficult due to lack of regular matrilineal family name information in many cultures (see Matrilineal family name).
Autosomal DNA combined with genealogical research has been used by people who were adopted to find their biological parents, have been used to find names and families of unknown bodies and by law enforcement agencies to catch criminals (eg, the offices of Contra Costa County District Attorneys use GEDmatch's "open-source" genetic site to find relatives of suspects in the Golden State Killer case.). The Atlantic magazine commented in 2018 that "Now, the gates open... a small website run by volunteers, GEDmatch.com, has become... a de facto DNA database and genealogy for all law enforcement.
Weakness
General concerns about genealogical DNA testing are a matter of cost and privacy. Some test companies store samples and results for their own use without a privacy agreement with the subject.
Autosomal DNA testing can identify relationships with good accuracy up to about 2nd cousins, but they have limitations. In particular, stem cell or bone marrow transplantation will produce matches with donors. Additionally, identical twins (which have identical DNAs) will share a higher amount of DNA with larger relatives.
The testing of the father-to-child genealogy of Y-DNA can reveal complications, due to unusual mutations, secret adoptions, and false dads (ie, that the father is perceived in a generation rather than the father indicated by a written birth note). According to the Ancestry and Ancestry Testing Task Force of the American Society of Human Genetics, an autosomal test can not detect "large portions" of DNA from distant ancestors because it has not been inherited.
With the increasing popularity of the use of DNA testing for ethnic tests, uncertainty and errors in ethnic estimates is a weakness for genetic geneology. While ethnic estimates at the continental level should be accurate (with possible exceptions in East Asia and America), sub-continent estimates, especially in Europe, are often inaccurate. Customer may be misinformed about uncertainty and forecast errors.
Some have recommended government or other ancestor testing rules to ensure their performance to an agreed standard.
A number of law enforcement agencies are trying to force genetic genealogy companies that store customer data to provide information to their customers who can match crime victims or perpetrators of cold crimes. A number of companies are fighting for the request.
Medical information
Although the results of genealogical DNA testing generally have no informative medical value and are not intended to determine genetic disease or disorder, the correlation exists between the lack of DYS464 markers and infertility, and between haplogroup H mtDNA and protection of sepsis. Certain haplogroups have been associated with longevity in some population groups. 23andMe provides medical information and the nature of their genealogical DNA tests and with a Promethease website charge analyzes genealogical DNA test data from Family Tree DNA, 23andMe, or AncestryDNA for medical information.
Full mtDNA sequencing testing is still somewhat controversial as it may reveal medical information. The disequilibrium linkage field, an association of genetic disorders that are not the same as certain mitochondrial lineages, is still in its infancy, but the associated mitochondrial mutations can be searched in the Mitomap genome database. Family Family The DNA's MtFull Sequence test analyzes the full MtDNA genome and the National Human Genome Research Institute operates the Genetic and Rare Disease Information Center that can assist consumers in identifying appropriate screening tests and help find the nearest medical center offering such a test.
DNA in genealogy software
Some genealogy software programs enable the recording of DNA marker tests, enabling tracking of Y-chromosome and mtDNA tests, and recording results for relatives. A family tree-DNA tree wall diagram is available.
See also
References
Further reading
External links
- Foundation and research project
- National Geographic Genographic Project
- Sorenson Molecular Genealogy Foundation
- Information and Map in haplogroup Y-DNA
- Y-haplogroup World Map
- Y-Haplogroup short description and origin of area
- Y-DNA Ethnographic and Genographic Atlas and Open Source Data Compilation
- DNA Testing: Y-haplogroup explained
Source of the article : Wikipedia
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