Ancestry DNA Testing
Ancestry DNA testing has become increasingly popular over the last few years. Individuals seek out DNA genetic testing for a variety of reasons. Some wish to reconnect with long-lost ancestors. Others want to find out if they're linked to any famous or historical figures. And some wish to fill gaps in their family history or locate living family members they may not have known otherwise.
However, some scientists scoff at DNA testing for genealogy. They argue that the margin of error is too great or that the legacy of relatives several generations back may be too weak to show up. But these criticisms don't stop the thousands of people who seek out DNA genetic testing each year.
Ancestry DNA Test Process
DNA genealogy testing typically costs between $100 and $900 and usually takes place through a DNA-testing firm. The firm takes microscopic tissue samples by swabbing the cheeks and gums on the inside of the client's mouth, and sends the samples to a laboratory for testing. The lab extracts and digitizes the DNA, and sends the results back to the firm. The firm then uses computer software to find matches between the client's DNA and those in their databases.
The genealogy DNA test generally comes in two forms. The first one examines mitochondrial DNA, which can uncover only information passed along through the client's maternal line. It cannot test any DNA from ancestral males.
The second form looks at the Y chromosome, which provides information exclusively from the paternal line. Only male clients can take the Y-chromosome test.
Some companies are currently experimenting with a test that examines the DNA contributions of both parents. However, many scientists believe that these tests are unreliable because of a lack of data.
When taken together, mitochondrial and Y-chromosome DNA genetic testing reveal information regarding about one percent of the client's DNA. It doesn't sound like much, but this information can uncover a lot about a person's ancestry, especially when used in combination with other genetic-research tools.
Accuracy of Genealogy DNA Testing
DNA testing for ancestry has come under criticism from scientists who feel that DNA ancestral tests are unreliable. Limited information in the DNA-testing firms' databases may cause clients to misinterpret results. Sometimes the tests can trace only a few of the client's ancestors.
Worse, genetic-testing firms don't always give clients the whole story. In 2007, the San Francisco Chronicle ran a story on a man who was tested in 2000 and told that his ancestry could be traced back to the Nubian ethnic group in Egypt. Five years later, he was tested again by a different company who told him that his ancestors were most likely European, not African. The first company had failed to tell him that he had multiple genetic matches—most of which were in Europe.
For these reasons, DNA genetic testing is most reliable when combined with another form of genealogical research method, such as searching through census records or birth and death certificates.
Accuracy for Y-chromosome tests can be improved by testing for more markers. These test results include Y-DNA alleles—a series of numbers showing how many times a pattern is repeated at a particular location (marker) on a chromosome. Testing for more markers can yield fewer results, but more accurate matches.
Resources
Harmon, A. (2006). Seeking ancestry in DNA ties uncovered by tests. Retrieved August 27, 2008, from the New York Times Web site: http://www.nytimes.com/2006/04/12/us/
12genes.html?_r=1&oref=slogin.
Nixon, R. (2007). DNA ancestry testing leaves some in doubt: Former proponents question the accuracy of the science. Retrieved August 27, 2008, from the San Francisco Chronicle Web site: http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2007/12/02/MNPQTIG6U.DTL.
Smolenyak, M. (2003). DNA testing: Why markers matter. Retrieved August 27, 2008, from the Ancestry.com Web site: http://www.ancestry.com/learn/library/article.aspx?article=6806.
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