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DNA Testing for Genealogical Research

It seems that everyday there are multiple news articles regarding DNA and how it is used to solve a crime, make a new medical discovery, help an adoptee find their biological parents, or any number of other subjects. Just as DNA is used as a tool in these situations, it can now be used by genealogists to help uncover the truth of family rumors, find new relatives, provide clues to new avenues of research and break through brick walls. Although genetic testing should not be used as a replacement for accurate genealogical research, it can often provide answers and evidence for theories in cases where conventional records do not exist.

Types of DNA Tests
There are many types of DNA tests – some are useful to solve crimes, others are useful in diagnosing medical conditions, and still others are useful for genealogists. In many cases, the results from the tests are not cross compatible. It is important to note that there is not a single “DNA test” that an individual can have done and/or that will answer all of the questions a person may have about their DNA.* We will describe the three types of DNA tests that are useful for genealogical research purposes, and give limited examples of situations where testing might be useful. We note that these tests generally provide information regarding “ancient” origins or the ethnicity of ancestors who lived several hundred to thousands of years ago. We will focus on the application of these test results for making genealogical, rather than anthropological, connections.
* There is one “DNA Test” that will answer every question. This would be a complete sequence of a person’s entire genome. The cost of this test is approximately $7000, and it cannot be ordered through any of the DTC testing companies at this time.

yDNA Test (paternal lineage)
yDNA tests have been in use for genealogical purposes for over 10 years. They are the most common type of DNA tests used in genealogical research, and the type of test that most individuals are familiar with. yDNA tests get their name from the Y-chromosome. The Y-chromosome is unique to men, and is what confers “maleness” on a person. It is passed virtually intact from father to son in a patrilineal fashion. In many cultures, surnames are also passed from father to son in this same way. Because only men have a y-chromosome, only men can take a yDNA test.
yDNA Testing
A yDNA test can be particularly useful for answering questions about a surname and its origins, or the relationship between two individuals who have a shared surname, but no proven genealogical connection. Based on the strength of the match between two individuals who have taken a y-DNA test, fairly accurate estimations regarding how long ago a common recent ancestor lived can be made, giving clues to time periods and geographical areas to research in order to break through brick walls, or identify new avenues of research. Due to the nature of the DNA markers used in this type of testing, the estimations regarding how long ago a common ancestor lived are generally within a genealogical time frame of 8-10 generations, and sometimes less.

Currently, there is only one DNA testing company that we can recommend for a yDNA test – Family Tree DNA in Houston, Texas. They offer yDNA tests starting with as low as 12 markers, and prices increase based on the number of markers tested. In most cases a 12-marker test does not provide enough information to
answer genealogical questions, and we generally recommend testing at least 37 markers. Tests for 67 and 111 markers are also available if further refinement regarding matches is necessary.

mtDNA Test (maternal lineage)
The mtDNA test is similar in many ways to a yDNA test. “mt” is short for mitochondrial, which identifies where in the cell this type of DNA is located, which is in the mitochondria. All other DNA is located in the nucleus of the cell. mtDNA is passed from a mother to all of her children, therefore can be taken by women and men. mtDNA is never passed on to children from their father. mtDNA testing provides specific information about an individual’s direct maternal line.
mtDNA Testing
mtDNA testing is not as useful as yDNA testing for genealogical purposes for a couple of reasons. The first reason is that it is not associated with a surname. The surname on a direct matrilineal line changes at each generation based on marriage and the custom of women assuming their husband’s surname. The second reason is that even if there is a perfect match between two individuals, often the time to their most recent common ancestor is as many as 15-20 generations. Except for royalty, records that would be able to identify the genealogical trail to this shared common ancestor do not often exist.

mtDNA testing can be useful in situations to confirm hypotheses regarding the origins of a direct maternal ancestor. The most common example of this is to identify a suspected Native American connection for a person’s direct maternal ancestor. Recently, there were articles in the news media announcing Prince William of Great Britain had Indian ancestry. mtDNA testing was employed in order to make this statement to identify a suspected Native American connection for a person’s direct maternal ancestor. Recently, there were articles in the news media announcing Prince William of Great Britain had Indian ancestry. mtDNA testing was employed in order to make this statement
and draw these conclusions. mtDNA testing has also been useful in cases where a man had multiple wives and it is unclear which wife was the mother of a certain child (as long as the women were not sisters or maternal cousins). Again, we recommend Family Tree DNA for mtDNA testing.

atDNA Test (for both paternal and maternal lineage)
atDNA or autosomal DNA tests are designed to look at over 700,000 DNA markers that can be found on a person’s “autosomes,” which are the 22 pairs of non-sex chromosomes found inside the nucleus of a cell. Because autosomal DNA is inherited from all of a person’s ancestors (up to at least 5 generations, sometimes more), it can be used to confirm recent relationships and provide clues to new research avenues for ancestors even further back in time. Parents pass on a random 50% of their autosomal DNA to each of their children. This happens at each generation, so on average, a person will have 12.5% of their great-grandparents’ DNA. This percentage is cut in half at each generation. The technology used in atDNA testing is fairly new, and is very powerful. An atDNA test can be taken by anyone, male or female. The results of an atDNA test provide information about a person’s ethnicity or “admixture” and a list of genetic cousins with whom a person shares a common ancestral couple.
atDNA Testing
The atDNA tests offered by the companies listed below are run on the same basic laboratory platform. The raw data/results from each company should not be significantly different, unless there is a laboratory error. The differences between the tests/companies are a result of the algorithms developed by each company to process the data and predict ethnicities and matches to genetic cousins. The algorithms to predict ethnicities are still being developed, as the science is fairly new. Therefore, there are often discrepancies between the ethnicity results between each company. It is worth noting that these companies are all continuing to adjust and revise their ethnicity algorithms, so a person’s ethnicity results may appear to change over time. This does not mean that the “raw data” has changed, only that the science has improved and is providing better analysis. Each company also has a different database of subscribers, which will lead to matches with different “genetic” cousins. There are advantages and disadvantages that should be considered when determining which company to test with.
Family Tree DNA
Family Finder is the atDNA test offered by Family Tree DNA. Many “genetic genealogists” prefer to test with FTDNA as their subscribers are generally the most responsive when it comes to sharing information (GEDCOM files, genealogical research data, etc.) to identify common ancestry, and work through brick-wall research questions. FTDNA also provides several advanced analysis tools that are necessary to truly confirm a suspected match with genetic cousins.

Family Tree DNA allows transfers of the raw data results into their database from 23andMe and AncestryDNA. Results transfers are not available through the other two companies. The last advantage to the Family Finder test is that it is done with a cheek swab, which is often easier to use than the “spit kit” used by the other two companies. Spit kits are often very difficult for older individuals to use.

In addition to testing markers of genealogical significance, 23andMe also tests for 250,000 additional markers that provide information regarding a person’s susceptibility to various genetic diseases and other traits. It is important to note that because of the medical information provided by 23andMe, individuals who live in New York or Maryland cannot take a 23andMe test. Because the other two companies do not offer medical information, individuals in these states can take an autosomal DNA test through one of them.

Many of 23andMe’s subscribers have tested for medical reasons, rather than genealogical reasons. Therefore, the response rate to inquiries regarding shared genealogical connections is often quite low, which can be frustrating when working on shared ancestral connections or “brick-wall” questions. Most “genetic genealogists” find 23andMe’s ethnicity predictions to be the most accurate of the three companies. 23andMe also provides multiple, excellent tools that allow one to work with the data and make new medical and genealogical discoveries. The most common recommendation by genetic genealogists is to test with 23andMe and then transfer the results to FTDNA in order to take full advantage of the benefits of both companies and the tools each provides.

The primary advantage to testing through AncestryDNA is that match results are often linked to family trees. AncestryDNA “does the work” of identifying a common ancestor between two individuals if that person can be located in both trees by’s computer algorithms. If a common ancestor cannot be located, then AncestryDNA provides a list of surnames and locations that are “in common” between the two trees. For the other two companies, this process is not automatic, and must be done by manually reviewing family trees and GEDCOM files for those on the match list.

AncestryDNA is not available outside of the United States; therefore, most of the individuals in their database are “Americans”. If the test-taker’s ancestors have been in the United States since the mid 19th century or so, then often there are significant high quality matches in Ancestry’s database. If the test-taker or his ancestors are fairly recent immigrants to the United States, then often there are few matches of much significance for them.

AncestryDNA lacks several tools that are necessary for confirming and tracking match results, and this is the primary disadvantage to testing with them. Ancestry does not provide a way to download a list of matches, making it difficult to track and remember which matches one has communicated with. AncestryDNA also does not provide a way to view the shared DNA segments between two individuals. The DNA segment information is necessary to confirm potential matches identified through analysis of family trees. Both 23andMe and FTDNA provide these tools.
GEDMatch is not a DNA testing company, but is mentioned here as it is a valuable resource for those who have taken an atDNA test. GEDMatch is a free website funded by donations and run by volunteers that allows for the upload of atDNA test results from any of the testing companies. This ability can be very valuable when reviewing matches between companies. It is also particularly valuable for those who have tested with AncestryDNA to confirm matches using DNA segment data, which is not provided by AncestryDNA. There are also triangulation features allowing comparison of genealogical (GEDCOM files) and genetic data available at GEDMatch. However, these features have had to be taken offline due to a large number of uploads from AncestryDNA customers (2013). Lastly, GEDMatch provides several tools for ethnicity and admixture analysis.

Just as there is no “one size fits all” genealogical record to answer research questions about an ancestor, there is no “one size fits all” DNA test to answer these genealogical questions, either. We recommend that there be a specific genealogical objective or research question in mind prior to completing a DNA test, just as there should be a specific objective in mind when undertaking traditional research. Once this question or objective is determined, then advice regarding which test to take, who should take the test, and with which company can be given. In some cases, good, old-fashioned genealogical research may provide the best answers to the questions being asked. In other cases, DNA may provide the only evidence or proof of suspected relationships and answers to questions. In most cases, both genealogical research and analysis of DNA testing results are combined to provide solid proof arguments regarding genealogical research questions.

DNA testing has been generally viewed as cost prohibitive for most genealogical research questions. However, with the recent drop in price for many of the tests, DNA testing is now something that can be used to confirm hypotheses and make new discoveries only dreamt of a few short years ago.

As genetic testing is a fairly new and rapidly evolving tool in the genealogists “toolbox”, we recommend the following websites and blogs for further information and answers to questions regarding DNA testing for genealogical purposes:

ISOGG (International Society of Genetic Genealogists) wiki –
ISOGG Facebook page -
DNA Newbie board at Yahoo!
CeCe Moore’s blog –
Blaine Bettinger’s blog –
Roberta Estes’ blog –
Rebekah Canada’s blog -
Judy Russell’s blog –

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