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Genealogical DNA test

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A genealogical DNA test involves examining the nucleotides at specific locations on a person's DNA. The tests results are meant to have no informative medical value and do not determine specific genetic diseases or disorders (see possible exceptions in Medical information below); they are intended only for use in genetic genealogy.

Procedure

The general procedure for taking a genealogical DNA test involves taking a painless cheek-scraping 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 offer to store DNA samples for ease of future testing. All 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. Other tests attempt to determine a researcher's comprehensive genetic history and ethnic origins.

Y chromosome (Y-DNA) testing

A man's paternal ancestry can be traced using the DNA on his Y chromosome (Y-DNA). This is useful because the Y chromosome, like many European surnames, passes from father to son, and can be used to help study surnames.

What gets tested

Y-DNA testing involves looking at segments of DNA on the Y chromosome (found only in males). Test results will be for a combination of short tandem repeats (STRs) and/or single nucleotide polymorphisms (SNPs). These genetic markers occur in what is considered "junk" DNA.

STR markers

STRs are changes to the number of times a segment of DNA which repeats. These repeating sets of nucleotides are referred to as genetic markers and are designated by a DYS number (DNA Y-chromosome Segment number).

SNP markers

SNPs are changes to a single nucleotide in a DNA sequence. The relative mutation rate for a SNP is extremely slow. 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 group who uses the letter M.

Understanding test results

Commonly y-DNA tests test ten to sixty-seven STR markers on the Y chromosome but over one-hundred markers are available. SNP tests STR test results provide your personal haplotype. SNP results indicate your Haplogroup.


Haplotype

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 high resolution 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 on 37 markers, there is a 50% probability that the MRCA was fewer than 5 generations ago and a 90% probability that the MRCA was fewer than 17 generations ago.

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

It is important to check the number of markers that will be tested before choosing a test. For example, the Genographic Project only looks at 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 for the Y chromosome, though this can only be confirmed by specifically testing for that Haplogroups' single nucleotide polymorphisms (SNPs). For example, at DYS455, the results will show 8, 9, 10, 11 or 12 repeats[1].

Haplogroup

Haplogroups are large groups of haplotypes that can be used to define genetic populations and are often geographically oriented. yDNA Haplogroups are determened by SNP tests.

These 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 SNP.

Haplogroup prediction

A person's haplogroup can often be inferred from their haplotype, but can only be proven 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:

DYS 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 probably a member of haplogroup N3 or E3b

Mitochondrial DNA (mtDNA) testing

Map of human migration, 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, harboring the start of the migration, is at the top left and South America is at the far right.

A person's maternal ancestry can be traced using his or her Mitochondrial DNA (mtDNA). The DNA in the human mitochondria is passed down by the mother unchanged. One exception, which was linked to infertility, has been shown.

What gets tested

mtDNA by current conventions is divided into three regions. They are the coding region and two Hyper Variable Regions (HVR1 and HVR2). All test results are compared to the mtDNA of a European in Haplogroup H2b. This sample is known as the Cambridge Reference Sequence (CRS). A list of single nucleotide polymorphisms (SNPs) is returned. Any "mutations" or "transitions" that are found are simply differences from the CRS. The test results are compared to another person's results to determine the time frame in which the two people shared a most recent common ancestor (MRCA). The two most common mtDNA tests are a sequence of HVR1 and a sequence of both HVR1 and HVR2. Some people are now choosing to have a full sequence performed. This is still somewhat controversial as 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 16001-16569. Some test reports might omit the 16 prefix from HVR1 results. ie 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 073-577.

Region HVR1 HVR2
Differences from CRS 111T,223T,259T,290T,319A,362C 064T,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.

Ethnic tests

Autosomal tests that test the recombining chromosomes are available. These attempt to measure an individual's mixed ethnic heritage. The tests' validity and reliability have been called into question but they continue to be popular.

Biogeographical ancestry

Autosomal DNA testing purports to determine the "genetic percentage" of certain ethnicities in a person. These tests examine SNPs, which are locations on the DNA where one nucleotide has "mutated" or "switched" to a different nucleotide. These tests are designed to tell what percentage Native American, European, East Asian, and African a person is. These tests are controversial—their validity has not been independently confirmed — and the results are often disputed.

One company[2] describes these four ethnic groups as follows:

  • Native American: Populations that migrated from Asia to inhabit North, South and Central America.
  • European: European, Middle Eastern and South Asian populations from the Indian subcontinent, including India, Pakistan and Sri Lanka.
  • East Asian: Japanese, Chinese, Mongolian, Korean, Southeast Asian and Pacific Islander populations, including populations native to the Philippines.
  • African: Populations from Sub-Saharan Africa such as Nigeria and Congo region.

A personal genetic analysis can be performed by one company[3] that 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 twenty three world regions:

  • Alaskan: Inuit peoples of Alaska.
  • Athabaskan: Athabaskan speaking peoples of Western North America.
  • Northeast Amerindian: Native peoples of Northeastern North America.
  • Salishan: Salish speaking peoples of the American Pacific Northwest.
  • South Amerindian: Native peoples of South America.
  • Mestizo (“mixed”): Native Americans blended with Europeans and Africans.
  • Arabian: The Arabian Peninsula.
  • Asia Minor: The East Mediterranean and Anatolia to the Tarim Basin.
  • North African: North Africa.
  • North Indian: Northern India.
  • South Indian: Southern India.
  • Sub-Saharan African: Africa south of the Sahara Desert.
  • Eastern European: The Slavic speaking region of Eastern Europe.
  • Basque: The Basque speaking peoples of Western Europe.
  • Finno-Ugrian: The Uralic speaking region of Northeastern Europe.
  • Mediterranean: The Romance speaking region of Southern Europe.
  • Northwest European: The Celtic and Germanic speaking region of Northwestern Europe.
  • Australian: Aboriginal peoples of Australia.
  • Chinese: The Chinese region of East Asia.
  • Japanese: The Japanese Archipelago.
  • Polynesian: The Polynesian Islands.
  • Southeast Asian: Southeast Asia and the Malay Archipelago.
  • Tibetan: The Himalayas and Tibetan Plateau.

This 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 racial classifications.

Native American ancestry

Autosomal testing, Y-DNA, and mtDNA testing can also be conducted to determine Native American ancestry. A mitochondrial haplogroup determination test based on mutations in Hypervariable Region I + II may establish whether a person's direct female line belongs to one of the five recognized Native American haplogroups, A, B, C, D or X, with the inference that he or she is, in whole or part, Native American. Comparisons with tribal-specific haplotypes of the sort published by geneticists Ripan Malhi and Jason Eschleman of Trace Genetics[1] can further suggest tribal affiliation, though no federally-recognized tribe considers DNA as admissible evidence for enrollment. This is based rather on the demonstrable appearance of names of one's direct ancestors on tribal-specific Native American censuses prepared as the fallout of treaty making and relegation to reservations in the nineteenth century. Complicating factors are the Native American name controversy and recent evidence that indigenous North American mitochondrial haplogroups are not limited to the five named. Many Americans are just discovering their Native roots, however, and the small chance of belonging to one of the acknowledged lineages, particularly in the case of male lines, which were almost entirely eradicated by the process of history, does not deter some from attempting to validate their heritage with the goal of gaining admittance into a tribe. These tests, moreover, are ideal for adoptees with Native American blood, of which there are now many in U.S. and Canadian society because of past policies of assimilation.

African ancestry

African Ancestry offers Y-DNA and mtDNA testing to determine with which present-day African country the direct-line paternal lineage or direct-line maternal lineage shares its ancestry. A pioneer in this field is Rick Kittles, a co-director of the National Human Genome Research Institute. It is estimated that 30 percent of African American males have a European Y chromosome haplogroup. As for the mitochondrial haplotypes, African Ancestry, Kittles' Washington, D.C.-based company specializing in such tests, lists some 300 tribal affiliations and seeks to assign, within a certain measure of likelihood, an African tribe to testees. Thus, Oprah Winfrey, the television talk show host, announced that she had discovered her Zulu roots. Zulu heritage from southern Africa must be counted as extremely rare, however, since according to authorities like Salas, nearly three-quarters of the ancestors of African Americans taken in slavery came from West Africa and most of these were Bantu. The African American tribal movement, however, has burgeoned since DNA testing, with members of African American churches taking the test as groups. One reason is that owing to slavery, African Americans cannot easily trace their ancestry through surname research, census and property records and other traditional means.

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 set of markers which determine Cohanim ancestry are known as the Cohen Modal Haplotype. This hypothetical ancestor of the Cohanim is called Y-chromosomal Aaron.

The whole field of Y chromosome DNA testing began with a Canadian doctor's discovery that an overwhelming majority of Jewish males with the surname Cohen (Hebrew for “priest”) had the same, or approximately the same set of markers, suggesting they truly descended from an original founder-priest like Aaron.

European testing

European maternal clan testing

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 is simply an mtDNA haplotype test based on the research in the book The Seven Daughters of Eve.

Sub-European population testing

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

  • Northern European subgroup (NOR) - mostly Northern European or Irish
  • Southeastern European (Mediterranean) subgroup (MED) - mostly Southeastern Europeans (Greeks 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

One company uses a 37-marker Y-DNA test which it says can be used to "verify genetic relatedness and historical gotra genealogies for Hindu and Buddhist engagements, marriages and business partnerships." 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. There are 49 established gotras.

Melungeon testing

Main article: Melungeon § DNA testing

Several efforts, including a number of ongoing studies, have examined the genetic makeup of families historically identified as Melungeon. Most results point to a mixture of European, African, and Native American lineages.

Benefits

Main article: Genetic genealogy

Genealogical DNA tests have become popular due to the ease of testing at home and the various additions they make to genealogical research. Genealogical DNA tests allow for an individual to determine with 99.9% certainty that he or she is related to another person within a certain time frame, or with 100% certainty that he or she is not related. DNA tests are perceived as more scientific, conclusive and expeditious.

Drawbacks

Y-DNA and mtDNA testing each only trace a single lineage (one's father's father's father's etc. lineage or one's mother's mother's mother's etc. lineage). At 10 generations back, an individual has 1024 ancestors (excluding intermarriages) and a Y-DNA or mtDNA test is only studying one of those 1024 ancestors. However, families in the past married in-group and breeding pools were typically small, so the paternal line can be diagnostic of additional ancestry.

The most common complaint from DNA test customers is failure of the company to make results understandable and meaningful to them. This was the No. 1 reason cited for customer dissatisfaction in a June 2006 nationwide telephone survey conducted by Shapiro and Associates. According to an earlier survey, 1 in 6 Americans (18%) said they were aware of the ancestry-tracing capability of a home DNA test but when probed, most knew little about the details, reliability or differences between tests.

A further drawback, at least with autosomal tests is their present state of imperfection and large margin of error (up to 15%, according to some genomics experts), with significant blind spots such as confusion of Mongolian ancestry with Native American.

Medical information

Though genealogical DNA tests results generally have no informative medical value and do not determine genetic diseases or disorders, there has been a correlation established between a lack of DYS464 markers and infertility, and a correlation between mtDNA haplogroup H and protection from sepsis. Certain haplogroups have been linked to longevity. A more specific test is used for medical purposes, which focuses on a particular gene or set of genes. 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. The National Human Genome Research Institute operates a Genetic And Rare Disease Information Center (GARD) that can assist consumers in identifying an appropriate screening test and help locate a nearby medical center that offers such.

  1. ^ Ybase statistics
  2. ^ AncestryByDNA
  3. ^ http://www.dnatribes.com/

Carmichael, Terrence and Alexander Kuklin (2000). How to DNA Test Our Family Relationships. DNA Press. Early (and still unique) book on adoptions, paternity and other relationship testing. Carmichael is a founder of GeneTree.

Cavalli-Sforza, L. et al (1994). The History and Geography of Human Genes. Princeton: Princeton University Press. Dense but very comprehensiven.

Cavalli-Sforza, Luigi-Luca and Francesco (1998). The Great Human Diasporas, translated from the Italian by Sarah Thorne. Reading, Mass. : Perseus Books. More readable than the Stanford professor’s other books.

Family Tree Magazine. Leading non-specialist genealogy magazine, reviews genetic genealogy products and companies from time to time.

Fitzpatrick, Colleen and Andrew Yeiser (2005). DNA and Genealogy. Rice Book Press. Highly regarded commentary on news stories about DNA and how-to introduction for laymen.

Gamble, Clive (1993). Timewalkers: The Prehistory of Global Colonization. Stroud: Sutton. Popular account of human prehistory by British anthropologist/archeologist. Article from American Scientist.

Hart, Anne - How to Interpret Family History & Ancestry DNA Test Results for Beginners, includes books, online articles and videos on genetic genealogy by this journalist and author

Howells, Cyndi (n.d.). Netting Your Ancestors – Genealogical Research on the Internet. Baltimore: Genealogical Publishing Company. Guide to electronic sources by author of Cyndi’s List website.

Jobling, M. (2003). Human Evolutionary Genetics. Standard college and graduate school level textbook by leading expert.

Kerchner, Charles F. Jr. (2004). Self-published. Genetic Genealogy DNA Testing Dictionary. Lookup source for esoteric terminology used.

Olson, Steve (2002). Mapping Human History. Boston: Houghton Mifflin Company. Survey of major populations.

Oppenheimer, Stephen (2003). The Real Eve. Modern Man’s Journey out of Africa. Carroll & Graf. Champions the “beachcomber route” theory with much technical detail.

PBS (2003). The Journey of Man DVD. Broadcast aired in January of 2003, Spencer Wells, host.

Panther-Yates, Donald and Elizabeth Caldwell Hirschman (2006). “DNA Haplotyping and Diversity: An Anthropogenealogical Method for Researching Lineages and Family Ethnicity,” International Journal of the Humanities 2:2043-55. Guide to finding matches in world databanks and interpreting genetic information in terms of history and recent emigration studies.

Pomery, Chris (2004) DNA and Family History: How Genetic Testing Can Advance Your Genealogical Research. London: National Archives. Early guide for do-it-yourself genealogists.

Savin, Alan (2003). DNA for Family Historians. Maidenhead: Genetic Genealogy Guides. Slim paperback first published in 2000, now available also in German.

Shawker, Thomas H. (2004). Unlocking Your Genetic History: A Step-by-Step Guide to Discovering Your Family's Medical and Genetic Heritage (National Geneological Society Guide, 6). Guide to the difficult subject of family medical history and genetic diseases.

Megan Smolenyak and Ann Turner (2005). Trace Your Roots with DNA: Using Genetic Tests to Explore Your Family Tree. Rodale Books. Recent tool for amateur genealogists by seminar speaker and DNA listserv moderator.

Sykes, Bryan (2001) The Seven Daughters of Eve. The Science that Reveals Our Genetic Ancestry. New York, Norton. Names the founders of Europe’s major female haplogroups Helena, Jasmine, Katrine, Tara, Velda, Xenia, and Ursula.

Sykes, Bryan (2004). Adam's Curse. A Future without Men. New York: W. W. Norton. The Oxford professor’s male sequel to The Seven Daughters of Eve.

Tagliaferro, Linda (1999). The Complete Idiot’s Guide to Decoding Your Genes. Alpha Books. Uses everyday language to explain the role genes play in shaping who we are. Light on genealogy and a bit outdated.

Wells, Spencer (2004). The Journey of Man. New York: Random House.

See also

Testing comparisons

Haplogroup prediction

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