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Genealogical DNA test

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For a non-technical introduction to genetics in general, see Introduction to genetics.
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A genealogical DNA test examines the nucleotides at specific locations on a person's DNA for genetic genealogy purposes. The test results are not meant to have any informative medical value and do not determine specific genetic diseases or disorders (see possible exceptions in Medical information below); they are intended only to give genealogical information. Genealogical DNA tests generally involve comparing the results of living individuals to historic populations.

Procedure

Hospital Corpsman 1st Class uses a swab to take a DNA sample from a Fireman aboard USS Iwo Jima (LHD 7)

The general procedure for taking a genealogical DNA test involves taking a painless cheek-scraping (also known as a buccal swab) at home and mailing the sample to a genetic genealogy laboratory for testing. Some laboratories use mouth wash or chewing gum instead of cheek swabs. Some laboratories, such as the Human Origins Genotyping Laboratory (HOGL) at the University of Arizona, offer to store DNA samples for ease of future testing. All United States laboratories will destroy the DNA sample upon request by the customer, guaranteeing that a sample is not available for further analysis.

Types of tests

The most popular ancestry tests are Y chromosome (Y-DNA) testing and mitochondrial DNA (mtDNA) testing, which test direct-line paternal and maternal ancestry, respectively. DNA tests for other purposes attempt, for example, to determine a person's comprehensive genetic make-up and/or ethnic origins.

Y chromosome (Y-DNA) testing

A man's patrilineal ancestry, or male-line ancestry, can be traced using the DNA on his Y chromosome (Y-DNA) through Y-STR testing. This is useful because the Y chromosome passes down almost unchanged from father to son, i.e., the non-recombining and sex-determining regions of the Y chromosome do not change. A man's test results are compared to another man's results to determine the time frame in which the two individuals shared a most recent common ancestor or MRCA. If their test results are a perfect, or nearly perfect match, they are related within genealogy's time frame.[1]

Each person can then look at the other's father-line information, typically the names of each patrilineal ancestor and his spouse, together with the dates and places of their marriage and of both spouses' births and deaths. This information table will be referred to again within the mtDNA testing section below as the (matrilineal) "information table". The two matched persons may find a common ancestor or MRCA, as well as whatever information the other already has about their joint patrilineal ancestry prior to the MRCA—which might be a big help to one of them.[2] Or if not, both keep trying to extend their patrilineal ancestry further back in time. Each may choose to have their test results included in their surname's "Surname DNA project". And each receives the other's contact information if the other chose to allow this. They may correspond, and may work together in the future on joint research.[3]

Women who wish to determine their direct paternal DNA ancestry can ask their father, brother, paternal uncle, paternal grandfather, or a cousin who shares a common patrilineal ancestry (the same Y-DNA) to take a test for them.

What gets tested

Y-DNA testing involves looking at STR segments of DNA on the Y chromosome. The STR segments which are examined are referred to as genetic markers and occur in what is considered "junk" DNA.

STR markers

A Y-chromosome contains sequences of repeating nucleotides known as short tandem repeats (STRs). The number of repetitions varies from one person to another and a particular number of repetitions is known as an allele of the marker. Individual Y-DNA sequences or STRs which have proved useful in genealogical DNA work are called markers, and each has a name, such as DYS393 in the following example. (Names are assigned by the HUGO Gene Nomenclature Committee, and DYS means Y-DNA unique Sequence [or Segment] while 393 is this sequence's unique identification number – its identifier.)[4] This example states that the allele of Rumpelstiltskin's DYS393 marker is 12, also called the marker's "value". The value 12 means the DYS393 sequence of nucleotides is repeated 12 times—with a DNA sequence of (AGAT)12.

SNP markers

Strand 1 differs from strand 2 at a single base pair location (a C → T polymorphism).

A single-nucleotide polymorphism (SNP) is a change to a single nucleotide in a DNA sequence. The relative mutation rate for an SNP is extremely low. This makes them ideal for marking the history of the human genetic tree. SNPs are named with a letter code and a number. The letter indicates the lab or research team that discovered the SNP. The number indicates the order in which it was discovered. For example, M173 is the 173rd SNP documented by the Human Population Genetics Laboratory at Stanford University, which uses the letter M.

Understanding test results

Y-DNA tests generally examine 10-67 STR markers on the Y chromosome, but over 100 markers are available. STR test results provide the personal haplotype. SNP results indicate the haplogroup.

Haplotype

Further information: Y-chromosome haplogroups by populations

A Y-DNA haplotype is the numbered results of a genealogical Y-DNA test. Each allele value has a distinctive frequency within a population. For example, at DYS455, the results will show 8, 9, 10, 11 or 12 repeats, with 11 being most common.[5] For high marker tests the allele frequencies provide a signature for a surname lineage.

Kit Surname Haplo 3
9
3

  		3
9
0

  		1
9


  		3
9
1

  		3
8
5
a

 3
8
5
b

 4
2
6

  		3
8
8

  		4
3
9

  		3
8
9
-
1 		3
9
2

  		3
8
9
-
2 		4
5
8

  		4
5
9
a

 4
5
9
b

 4
5
5

  		4
5
4

  		4
4
7

  		4
3
7

  		4
4
8

  		4
4
9

  		4
6
4
a

 4
6
4
b

 4
6
4
c

 4
6
4
d

11111 Rumpelstiltskin Q 12 23 13 10 16 17 12 12 13 14 14 31 18 8 9 11 11 27 13 19 28 14 14 15 15

The test results are then compared to another project member's results to determine the time frame in which the two people shared a most recent common ancestor (MRCA). If the two tests match perfectly on 111 markers for members with the same surname, there is a 50% probability that the MRCA was fewer than 2 generations ago, 90% probability that it was fewer than 4 generations ago, and 95% probability it was fewer than 5 generations ago.[6]

Kit Surname Haplo 3
9
3

  		3
9
0

  		1
9


  		3
9
1

  		3
8
5
a

 3
8
5
b

 4
2
6

  		3
8
8

  		4
3
9

  		3
8
9
-
1 		3
9
2

  		3
8
9
-
2 		4
5
8

  		4
5
9
a

 4
5
9
b

 4
5
5

  		4
5
4

  		4
4
7

  		4
3
7

  		4
4
8

  		4
4
9

  		4
6
4
a

 4
6
4
b

 4
6
4
c

 4
6
4
d

11111 Rumpelstiltskin Q 12 23 13 10 16 17 12 12 13 14 14 31 18 8 9 11 11 27 13 19 28 14 14 15 15
11178 Rumpelstiltskin Q 12 23 13 10 16 17 12 12 13 14 14 31 18 8 9 11 11 27 13 19 28 14 14 15 15

Before choosing a test, it is important for an individual to check the number of markers that will be tested. For example, the Genographic Project looks at only 12 markers, while most laboratories and surname projects recommend testing at least 25. The more markers that are tested, the more discriminating and powerful the results will be. A 12-marker STR test is usually not discriminating enough to provide conclusive results for a common surname.

STRs results may also indicate a likely haplogroup, though this can only be confirmed by specifically testing for that Haplogroups' single-nucleotide polymorphisms (SNPs).

Haplogroup

File:Haplogroups europe.png
Y-DNA-haplogroups in Europe

Haplogroups are large groups of haplotypes that can be used to define genetic populations and are often geographically oriented.

Y-DNA haplogroups are determined by SNP tests. SNPs are locations on the DNA where one nucleotide has "mutated" or "switched" to a different nucleotide. The nucleotide switch must occur in at least 1% of the population to be considered a useful SNP. If it occurs in less than 1% of the population, it is considered a personal (or private) SNP.

Haplogroup prediction

A person's haplogroup can often be inferred from their haplotype, but can be proven only with a Y-chromosome SNP tests (Y-SNP test). In addition, some companies offer sub-clade tests, such as for Haplogroup G. For example, Haplogroup G has a known modal haplotype:

Y-STR markers 3
8
5
a 		3
8
5
b 		3
8
8
  		3
8
9
i 		3
8
9
ii 		3
9
0
  		3
9
1
  		3
9
2
  		3
9
3
  		3
9
4
  		4
2
6
  		4
3
7
  		4
3
9
  		4
4
7
  		4
4
8
  		4
4
9
  		4
5
4
  		4
5
5
  		4
5
8
  		4
5
9
a 		4
5
9
b 		4
6
4
a 		4
6
4
b 		4
6
4
c 		4
6
4
d
Haplogroup G: Modal STR values 14 14 12 12 29 22 10 11 14 15 11 16 11 23 21 31 11 11 16 9 9 12 13 13 14

Few haplotypes will exactly match the modal values for Haplogroup G. One can consult an allele frequency table to determine the likelihood of remaining in Haplogroup G based on the variations observed.

Additional predictions include:

  • If DYS426 is 12 and DYS392 is 11, one is probably a member of haplogroup R1a1.
  • If DYS426 is 12 and DYS392 is not 11, one is probably a member of haplogroup R1b.
  • If DYS426 is 11, one is probably a member of haplogroup G,I, or J.
  • If DYS426 is 11 and DYS388 is 12, one is in the known modal haplotype for G shown above.

A Bayes classifier to predict the haplogroup probabilities for an observed haplotype is available on the web: Whit Athey Haplogroup Predictor.

Mitochondrial DNA (mtDNA) testing

Map of human migration out of Africa, according to Mitochondrial DNA. The numbers represent thousands of years before present time. The blue line represents the area covered in ice or tundra during the last great ice age. The North Pole is at the center. Africa, the center of the start of the migration, is at the top left and South America is at the far right.

A person's matrilineal or mother-line ancestry can be traced using the DNA in his or her mitochondria, the mtDNA, as follows: This mtDNA is passed down by the mother unchanged, to all children. If a perfect match is found to another person's mtDNA test results, one may find a common ancestor in the other relative's (matrilineal) "information table", similar to the patrilineal or Y-DNA testing case above. However, because mtDNA mutations are very rare, a nearly perfect match is not as helpful as it is for the above patrilineal case. In the matrilineal case, it takes a perfect match to be very helpful.[7]

Note that, in cultures lacking matrilineal surnames to pass down, neither relative above is likely to have as many generations of ancestors in their matrilineal information table as in the above patrilineal or Y-DNA case: for further information on this difficulty in traditional genealogy, due to lack of matrilineal surnames (or matrinames), see Matriname.[8]

Some people cite paternal mtDNA transmission as invalidating mtDNA testing,[9] but this has not been found problematic in genealogical DNA testing, nor in scholarly population genetics studies. See the rest of this article.

What gets tested

mtDNA by current conventions is divided into three regions. They are the coding region (00577-16023) and two Hyper Variable Regions (HVR1 [16024-16569], and HVR2 [00001-00576]).[10] All test results are compared to the mtDNA of a European in Haplogroup H2a2a. This early sample is known as the Cambridge Reference Sequence (CRS). A list of single nucleotide polymorphisms (SNPs) is returned. The relatively few "mutations" or "transitions" that are found are then reported simply as differences from the CRS, such as in the examples just below.

The two most common mtDNA tests are a sequence of HVR1 and a sequence of both HVR1 and HVR2. Some mtDNA tests may only analyze a partial range in these regions. Some people are now choosing to have a full sequence performed, to maximize their genealogical help. The full sequence is still somewhat controversial because it may reveal medical information.

Understanding test results

The most basic of mtDNA tests will sequence Hyper Variable Region 1 (HVR1). HVR1 nucleotides are numbered 16024-16569.[11]

Examples
  • Some test reports might omit the "16" (16nnn) prefix from HVR1 results, i.e. 519C and not 16519C.
Region HVR1 HVR2
Differences from CRS 111T,223T,259T,290T,319A,362C Not Tested
  • More extensive tests will also sequence Hyper Variable Region 2 (HVR2). HVR2 nucleotides are numbered 00001-00576.[12]
Region HVR1 HVR2
Differences from CRS 111T,223T,259T,290T,319A,362C 073G,146C,153G

Haplogroup

Most results include a prediction of mtDNA Haplogroup.

Phylogenetic tree of human mitochondrial DNA (mtDNA) haplogroups

  Mitochondrial Eve (L)    
L0 L1–6  
L1 L2   L3     L4 L5 L6
M N  
CZ D E G Q   O A S R   I W X Y
C Z B F R0   pre-JT   P   U
HV JT K
H V J T

If you belong to a Haplogroup that is distantly related to the CRS, then the prediction may be sufficient. Some companies test for specific mutations in the coding region. For large Haplogroups, such as mtDNA Haplogroup H, an extended test is offered to assign a sub-clade.

Geographic origin tests

European genetic structure (based on Autosomal SNPs) by PCA

Autosomal tests that test the recombining chromosomes are available. These attempt to measure an individual's mixed geographic heritage by identifying particular markers, called ancestry informative markers or AIM, that are associated with populations of specific geographical areas. The tests' validity and reliability have been called into question but they continue to be popular.[13][14] Anomalous findings most often result from databases too small to associate markers with all the areas where they occur in indigenous populations.

Biogeographical ancestry

Autosomal DNA testing purports either to determine the "genetic percentages" of a person's ancestry from particular continents/regions or to identify the countries and "tribes" of origin on an overall basis. Admixture tests arrive at these percentages by examining SNPs, which are locations on the DNA where one nucleotide has "mutated" or "switched" to a different nucleotide. Tests' listing geographical places of origin use alleles—individual and family variations on various chromosomes across the genome analyzed with the aid of population databases. As further detailed below, this latter type of test concentrates on standard identity markers, such as the CODIS profile, combined with databases such as OmniPop, ENFSI and proprietary adaptations of published studies.

STR tests

In 2006, one company[15] developed an autosomal DNA ancestry-tracing product that combined the traditional CODIS markers used by law enforcement officers and the judicial system with OmniPop, a population database developed by San Diego detective Brian Burritt. Customers received matches to their profile's frequency of occurrence in world populations, as well as a breakout for European ancestry based on the European Network of Forensic Science Institutes (ENFSI).[16] As a public service, the company has supported the expansion of OmniPop, which currently encompasses over 360 populations, double that of its first release. The ENFSI calculator uses data from 24 European populations (5700 profiles). The two databases must be searched separately, because they are based on two different sets of markers. The company sells its product as the DNA Fingerprint Test. The 16 markers incorporated in its results are: D8S1179, D21S11, D7S820, CSFIPO, D3S1358, THO1, D13S317, D16S539, D2S1338, D19S433, VWA, TPOX, D18S51, D5S818, and FGA.

The theory behind using a forensic profile for ancestry tracing is that the alleles' respective frequency of occurrence develops over generations with equal input of the two parents, since for each location we take one value from our mother and one from our father. It thus serves as a window into a person's total ancestral composition. The configuration of scores reflects inherited changes from all previous generations in all ancestral lines, and can predict an individual's unique probable ethnic matches based on the profile's frequency or rarity in different populations.[17]

As studies from more populations are included, the accuracy of results should improve, leading to a more informative picture of one's ancestry.

Along the same lines, yet another company[18] identifies the indigenous and diaspora populations in which an individual's autosomal STR profile is most common. This test examines autosomal STRs, which are locations on a chromosome where a pattern of two or more nucleotides is repeated and the repetitions are directly adjacent to each other. The populations in which the individual's profile is most common are identified and assigned a likelihood score. The individual's profile is assigned a likelihood of membership in each of thirty-four world regions:[19]

The STR analysis measures the frequency of a person's DNA profile within major world regions. Unlike SNP admixture tests, this analysis is based on objectively identified world regions and does not depend on any system of presumed biogeographic classifications. As most STR analysis examines markers chosen for their high intra-group variation, the utility of these particular STR markers to access inter-group relationships may be greatly diminished.

SNP tests

The same company also provides since 2011 a geographical "deep ancestry" analysis that can be performed based on genotype raw data from any of several SNP microarray tests. The report includes both admixture and total similarity comparisons of one's DNA to world genetic structure. The report identifies ancestral contributions to one's genome from 7 continental zones (European, Middle Eastern, Sub‐Saharan African, East Asian, North Asian, South Asian, Native American) as well as from 20 world regions (Atlantic European, Caucasus‐Anatolian, Arabian, North African, Baltic-Urals, South India, Indus Valley, African Great Lakes, West African, Southern African, Horn of Africa, Southeast Asian, Chinese, Manchurian, Siberian, Arctic, Mongolian, Oceanian, Mesoamerican, ).

Sample Results (October 2011)[20][21]
Population (October 2011) Atlantic European Baltic-Urals Caucasus-Anatolian North African Arabian Indus Valley South India Siberian Arctic Mongolian Other
Adyghe 0.0% 1.7% 92.5% 0.0% 0.0% 4.4% 0.0% 0.3% 0.0% 1.1% 0.0%
Algeria 3.8% 0.1% 0.0% 86.0% 9.2% 0.0% 0.0% 0.0% 0.1% 0.0% 0.7%
Armenian 0.0% 0.0% 83.3% 0.0% 16.7% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Basque 92.6% 0.0% 0.0% 5.9% 1.5% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Belarus 27.2% 68.6% 4.2% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Bergamo 72.5% 0.0% 12.2% 3.2% 12.1% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Bulgaria 70.7% 0.0% 23.6% 0.0% 5.7% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Chuvash 0.0% 67.0% 5.2% 0.0% 0.0% 7.1% 0.0% 10.0% 3.9% 5.8% 0.9%
Cornwall 97.8% 2.1% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.1%
Cyprus 7.1% 0.0% 46.0% 0.0% 47.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Egypt 0.0% 0.0% 0.0% 8.8% 88.8% 0.0% 0.0% 0.0% 0.0% 0.0% 2.4%
England 94.1% 5.8% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.1%
Finland 0.0% 100.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
France 93.4% 0.0% 1.5% 1.4% 3.8% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Greece 36.5% 0.0% 51.4% 2.9% 9.2% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Hungary 66.8% 18.3% 5.6% 0.0% 2.8% 1.7% 2.1% 0.0% 0.0% 0.9% 0.0%
Ireland 86.6% 13.1% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.3%
Lebanon 0.8% 0.0% 43.8% 5.3% 45.7% 2.6% 0.0% 0.0% 0.0% 0.0% 1.7%
Lezgin 0.0% 4.2% 80.2% 0.0% 0.0% 15.6% 0.0% 0.0% 0.0% 0.0% 0.0%
Lithuania 0.0% 100.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Mordvin 0.0% 84.9% 8.7% 0.0% 0.0% 3.8% 0.0% 1.9% 0.0% 0.0% 0.8%
Nogay 0.1% 12.3% 59.9% 0.0% 0.0% 7.6% 0.0% 2.9% 1.4% 10.1% 5.7%
North Morocco 12.5% 0.0% 1.7% 85.8% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Orkney 88.5% 10.3% 0.0% 0.0% 0.0% 1.1% 0.0% 0.0% 0.0% 0.0% 0.2%
Portugal 71.3% 3.7% 1.2% 15.1% 8.4% 0.0% 0.0% 0.0% 0.0% 0.0% 0.3%
Romania 73.5% 7.5% 18.1% 0.0% 0.1% 0.0% 0.5% 0.0% 0.0% 0.1% 0.2%
Russia 29.3% 64.6% 4.3% 0.0% 0.0% 0.9% 0.0% 0.0% 0.0% 0.0% 0.9%
Sardinia 69.5% 0.0% 0.0% 9.8% 20.7% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Scandinavia 88.0% 10.8% 0.0% 0.0% 0.0% 0.1% 0.0% 0.0% 0.4% 0.0% 0.8%
Slovenia 74.4% 20.3% 5.1% 0.0% 0.0% 0.3% 0.0% 0.0% 0.0% 0.0% 0.0%
Southern Italy and Sicily 38.2% 0.0% 31.1% 2.0% 28.8% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Spain 86.4% 0.0% 0.0% 7.4% 6.3% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Tunisia 9.4% 0.0% 3.6% 87.1% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Turkey 0.0% 0.0% 84.4% 0.8% 9.8% 0.7% 1.4% 2.0% 0.0% 0.5% 0.5%
Tuscany 61.0% 0.0% 18.0% 0.3% 20.6% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Ukraine 31.8% 61.7% 5.6% 0.0% 0.9% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
Vologda 0.0% 95.4% 0.0% 0.0% 0.0% 1.4% 0.2% 2.2% 0.0% 0.0% 0.8%

United States

Because of its history of immigration, slavery, and significant indigenous peoples, people of the United States have been interested in using genealogical DNA studies to help them learn more about their ancestry.

United States - Native American ancestry

Further information: Genetic history of indigenous peoples of the Americas

Autosomal testing, Y-DNA, and mtDNA testing can be conducted to determine Amerindian ancestry. A mitochondrial Haplogroup determination test based on mutations in Hypervariable Region 1 and 2 may establish whether a person's direct female line belongs to one of the canonical Native American Haplogroups, A, B, C, D or X. If one's DNA belonged to one of those groups, the implication would be that he or she is, in whole or part, Native American.

As political entities, tribes have established their own requirements for membership, often based on at least one of a person's ancestors having been included on tribal-specific Native American censuses (or final rolls) prepared during treaty-making, relocation to reservations or apportionment of land in the late 19th century and early 20th century. One example is the Dawes Rolls. In addition, the U.S. government does not consider DNA as admissible evidence for enrollment in any federally recognized tribe or reception of benefits. Tribes are political constructs, not genetic populations.

The vast majority of Native American individuals do belong to one of the five identified mtDNA Haplogroups. Many Americans are just discovering they have some percentage of Native ancestry. Some attempt to validate their heritage with the goal of gaining admittance into a tribe, but most tribes do not use DNA results in that way. These tests may be useful for adoptees to discover Native American ancestry.

United States - African ancestry

Y-DNA and mtDNA testing may be able to determine with which peoples in present-day African country a person shares a direct line of part of his or her ancestry, but patterns of historic migration and historical events cloud the tracing of ancestral groups. Testing company African Ancestry[22] maintains an "African Lineage Database" of African lineages from 30 countries and over 160 ethnic groups. Due to joint long histories in the US, approximately 30% of African American males have a European Y chromosome haplogroup[23] Approximately 58% of African Americans have the equivalent of one great-grandparent (12.5 percent) of European ancestry. Only about 5% have the equivalent of one great-grandparent of Native American ancestry. By the early 19th century, substantial families of Free Persons of Color had been established in the Chesapeake Bay area who were descended from people free during the colonial period; most of those have been documented as descended from white men and African women (servant, slave or free). Over time various groups married more within mixed-race, black or white communities.[24]

According to authorities like Salas, nearly three-quarters of the ancestors of African Americans taken in slavery came from regions of West Africa. The African-American movement to discover and identify with ancestral tribes has burgeoned since DNA testing became available. Often members of African-American churches take the test as groups.[citation needed] African Americans cannot easily trace their ancestry during the years of slavery through surname research, census and property records, and other traditional means. Genealogical DNA testing may provide a tie to regional African heritage.

United States - Melungeon testing

Main article: Melungeon § DNA testing

Melungeons are one of numerous multiracial groups in the United States with origins wrapped in myth. The historical research of Paul Heinegg has documented that many of the groups in the Upper South were descended from mixed-race people who were free in colonial Virginia and descended from unions between the Europeans and Africans. They moved to the frontiers of Virginia, North Carolina, Kentucky and Tennessee to gain some freedom from the racial barriers of the plantation areas.[25] Several efforts, including a number of ongoing studies, have examined the genetic makeup of families historically identified as Melungeon. Most results point primarily to a mixture of European and African, which is supported by historical documentation. Some may have a very small amount of Native American lineages (none in one study). Though some companies provide additional Melungeon research materials with Y-DNA and mtDNA tests, any test will allow comparisons with the results of current and past Melungeon DNA studies.

General interest

Cohanim ancestry

Main article: Y-chromosomal Aaron

The Cohanim (or Kohanim) is a patrilineal priestly line of descent in Judaism. According to the Bible, the ancestor of the Cohanim is Aaron, brother of Moses. Many believe that descent from Aaron is verifiable with a Y-DNA test: the first published study in genealogical Y chromosome DNA testing found that a significant percentage of Cohens had distinctively similar DNA, rather more so than general Jewish or Middle Eastern populations. These Cohens tended to belong to Haplogroup J, with Y-STR values clustered unusually closely around a haplotype known as the Cohen Modal Haplotype (CMH). This could be consistent with a shared common ancestor, or with the hereditary priesthood having originally been founded from members of a single closely related clan.

Nevertheless, the original studies tested only six Y-STR markers, which is considered a low-resolution test. Such a test does not have the resolution to prove relatedness, nor to estimate reliably the time to a common ancestor. The Cohen Modal Haplotype (CMH), while notably frequent among Cohens, also appears in the general populations of haplogroups J1 and J2 with no particular link to the Cohen ancestry. So while many Cohens have haplotypes close to the CMH, many more of such haplotypes worldwide belong to people with no likely Cohen connection at all. According to researchers (Hammer), it is only the CMH that is found in J1 that is to be attributed to the Aaron lineage, not the CMH in J2. Jews with the CMH in both J1 and J2 cannot all be descended from one man who lived approximately 3,300 years ago, because J1 diverged from J2 10,000 years ago.

Resolution may be increased by the testing of more than six Y-STR markers. For some, this could help to establish relatedness to particular recent Cohen clusters. For many, the testing is unlikely to distinguish definitively shared Cohen ancestry from that of the more general population distribution. So far no published research indicates what extended Y-STR haplotype distributions appear to be characteristic of Cohens.

Although some high-resolution testing has been done, to date the results have not been released.

European testing

Further information: Genetic history of Europe

For people with European maternal ancestry, mtDNA tests are offered to determine which of eight European maternal "clans" the direct-line maternal ancestor belonged to. This mtDNA haplotype test was popularized in the book The Seven Daughters of Eve.

SNP testing may enable mostly European individuals to determine to which Sub-European population they belong:

  • Northern European subgroup (NOR) - mostly Northern and Southwestern European
  • Southeastern European (Mediterranean) subgroup (MED) - mostly Southeastern Europeans (Greeks, Albanians or Turks)
  • Middle Eastern subgroup (MIDEAS) - mostly Middle Eastern
  • South Asian subgroup (SA) - mostly South Asian from the Indian sub-continent (i.e. Indian)

Hindu testing

The 49 established gotras are clans or families whose members trace their descent to a common ancestor, usually a sage of ancient times. The gotra proclaims a person's identity and a "gotraspeak" is required to be presented at Hindu ceremonies. People of the same gotra are not allowed to marry.

One company says it can use a 37-marker Y-DNA test to "verify genetic relatedness and historical gotra genealogies for Hindu and Buddhist engagements, marriages and business partnerships." This has not been supported by independent research. Any Y-DNA test can be used to compare results with another person whose gotra is known.

Benefits

Main article: Genetic genealogy

Genealogical DNA tests have become popular due to the ease of testing at home and their supplementing genealogical research. Genealogical DNA tests allow for an individual to determine with high accuracy whether he or she is related to another person within a certain time frame, or with certainty that he or she is not related. DNA tests are perceived as more scientific, conclusive and expeditious than searching the civil records. But, they are limited by restrictions on lines which may be studied. The civil records are always only as accurate as the individuals who provided or wrote the information.

The aforementioned Y-DNA testing results are normally stated as probabilities: For example, with the same surname a perfect 37/37 marker test match gives a 95% likelihood of the most recent common ancestor (MRCA) being within 8 generations,[26] while a 111 of 111 marker match gives the same 95% likelihood of the MRCA being within only 5 generations back.[6]

As presented above in mtDNA testing, if a perfect match is found, the mtDNA test results can be helpful. In some cases, research according to traditional genealogy methods encounters difficulties due to the lack of regularly recorded matrilineal surname information in many cultures.(see Matrilineal surname).[8]

Drawbacks

Common concerns about genealogical DNA test are cost and privacy issues (some testing companies retain samples and results for their own use without a privacy agreement with subjects). The most common complaint from DNA test customers is the failure of the company to make results understandable to them.

DNA tests can do some things well, but there are constraints. Testing of the Y-DNA lineage from father to son may reveal complications, due to unusual mutations, secret adoptions, and false paternity (i.e. the father in one generation is not the father in birth records.) According to some genomics experts, autosomal tests may have a margin of error up to 15% and blind spots.[citation needed]

Some users have recommended that there be government or other regulation of ancestry testing to ensure more standardization.[27]

Medical information

Though genealogical DNA test results generally have no informative medical value and are not intended to determine genetic diseases or disorders, a correlation exists between a lack of DYS464 markers and infertility, and between mtDNA haplogroup H and protection from sepsis. Certain haplogroups have been linked to longevity.[28]

The testing of full mtDNA sequences is still somewhat controversial as it may reveal medical information. The field of linkage disequilibrium, unequal association of genetic disorders with a certain mitochondrial lineage, is in its infancy, but those mitochondrial mutations that have been linked are searchable in the genome database Mitomap.[29] The National Human Genome Research Institute operates the Genetic And Rare Disease Information Center[30] that can assist consumers in identifying an appropriate screening test and help locate a nearby medical center that offers such.

DNA in genealogy software

Some genealogy software programs now allow recording DNA marker test results, allowing for tracking of both Y-chromosome and mtDNA tests, and recording results for relatives. DNA-family tree wall charts are available.

See also

Main article: List of genetic genealogy topics

References

  1. ^ "Y-DNA matches". Smgf.org. Retrieved 15 June 2011.
  2. ^ "Here is one such case, see the heading "A success story quote"". Freepages.genealogy.rootsweb.ancestry.com. Retrieved 15 June 2011.
  3. ^ "Extending Family Trees with DNA Testing". Dna-testing-adviser.com. Retrieved 15 June 2011.
  4. ^ ftdna.com (kept uptodate). http://www.familytreedna.com/faq/answers/default.aspx?faqid=9#961 "FAQ: What do the DYS ... STR names mean?" Retrieved 2012-01-13.
  5. ^ "Ybase statistics". Ybase.org. 19 April 2011. Retrieved 15 June 2011.
  6. ^ a b ftdna.com (kept uptodate). http://www.familytreedna.com/faq/answers/default.aspx?faqid=9#925 "FAQ: ...how should the genetic distance at 111 Y-chromosome STR markers be interpreted?" Retrieved 2012-01-13.
  7. ^ "mtDNA matches". Smgf.org. Retrieved 15 June 2011.
  8. ^ a b Sykes, Bryan (2001). The Seven Daughters of Eve. W. W. Norton. ISBN 0-393-02018_5, pp. 291-92. Sykes discusses the difficulty in genealogically tracing a maternal lineage, due to the lack of matrilineal surnames (or matrinames).
  9. ^ for example: M. Pickford, "Paradise lost: Mitochondrial eve refuted", SpringerLink, July 2006
  10. ^ "mtDNA regions". Phylotree.org. Retrieved 15 June 2011.
  11. ^ "mtDNA HVR1 region". Phylotree.org. Retrieved 15 June 2011.
  12. ^ "mtDNA HVR2 region". Phylotree.org. Retrieved 15 June 2011.
  13. ^ Bolnick, DA et al. The Science and Business of Genetic Ancestry Testing. Science: Vol 318, 19 October 2007
  14. ^ Frudakis, T. The Legitimacy of Genetic Ancestry Tests. Science: Vol 319, 22 February 2008
  15. ^ "DNA Testing Systems". Dnaconsultants.com. 11 June 2011. Retrieved 15 June 2011.
  16. ^ "ENFSI DNA WG - STR Population Database". str-base.org. Retrieved 15 June 2011.
  17. ^ Balding, D.J. et al., eds. (2001). Handbook of Statistical Genetics, New York: Wiley
  18. ^ DNA Tribes
  19. ^ "Neighbor joining tree illustrating the relationships among world regions based on Euclidean distance" (PDF). Retrieved 15 June 2011.
  20. ^ Genetic Links between Three SNP Based Regions in Europe
  21. ^ Updated SNP Continent and Regional Admixture
  22. ^ "African Ancestry". African Ancestry. Retrieved 15 June 2011.
  23. ^ "Patriclan: Trace Your Paternal Ancestry". African Ancestry. Retrieved 15 June 2011.
  24. ^ Paul Heinegg, Free African Americans of Virginia, North Carolina, South Carolina, Maryland and Delaware[1], accessed 15 Feb 2008
  25. ^ Paul Heinegg, Free African Americans of Virginia, North Carolina, South Carolina, Maryland and Delaware, accessed 15 Feb 2008
  26. ^ ftdna.com (kept uptodate). http://www.familytreedna.com/faq/answers/default.aspx?faqid=9#922 "FAQ: ...how should the genetic distance at 37 Y-chromosome STR markers be interpreted?" Retrieved 2012-01-13.
  27. ^ Lee et al., "The Illusive Gold Standard in Genetic Ancestry Testing", Science 3, July 2009: 38-39
  28. ^ . PMID 10463944. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  29. ^ "Mitomap". Mitomap. Retrieved 15 June 2011.
  30. ^ "Genetic And Rare Disease Information Center (GARD)". Genome.gov. 22 March 2011. Retrieved 15 June 2011.

Further reading

Tutorials
Societies
Foundations and research projects
STR converters
Information and Maps on Y-DNA haplogroups

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