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Beyond the Paper Trail: Discovering Family History with Different DNA Tests

Molecular genealogy, the study of DNA to help genealogical research, has made big strides over the last few years, but some answers are still out of science's reach. Learn what you can and can't learn from the different genetic tests, and which ones may be right for you.


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DNA genealogy is letting genealogists trace their heritage beyond the end of the paper trail. But what can and can't this new science tell you, and which tests are right for you?

Maybe there are several families in your area with the same surname but no known common ancestor. Maybe your great-grandmother was rumored to be Native American but you can't find any supporting documentation. Maybe you just want to know where your ancestors came from before they began leaving a paper trail. These are cases where molecular genealogy can help shed some light.

"DNA provides a source of information about ancestry that is older and more fundamental than what is available from documentary family history," advised Lucas Martin of DNA Tribes. By studying and comparing DNA signatures, labs are able to prove relationships, suggest ethnicities and areas of origin, and suggest a sweeping back-story of your family across major historical events. "This adds a different element to what a person can learn," said Bennett Greenspan of Family Tree DNA.

Over the last five years, advances in science have increased the amount of information you can gain from some tests and have lowered the price on others. The most popular DNA genealogical tests right now are the following:

Y-DNA Testing: A Y-DNA test looks at the part of a man's Y chromosome that he inherits from his father, who inherited it from his father, and so on. Since this direct paternal line corresponds to the family surname, different families with the same surname can pool results in an effort to find their most recent common ancestor.

Since all males in the direct paternal line will share the same signature, the Y-DNA test cannot be used as a paternity test. In the famous case of Thomas Jefferson and Sally Hemings, a Hemings' male descendant was proven to have Jefferson Y-DNA. But science cannot prove which male Jefferson passed down his Y-DNA to Heming's descendants, continuing the controversy over whether Thomas Jefferson fathered Heming's children. Y-DNA tests range from $99 to $300.

Mitochondrial DNA (mtDNA) Testing: Mitochondrial DNA is carried by both men and women, but only women can pass it on to their children. While Y-DNA traces the direct paternal line, mtDNA traces the direct maternal line, that is, your mother's mother's mother and so on.

While an mtDNA test can reveal deep ancestral origins, it is generally not as good for genealogical research. Scientists differentiate between different groups of people based on how often DNA mutations occur. Since mtDNA mutations happen slowly, sometimes over thousands of years, "a match on the mtDNA could refer to a common ancestor far back in time," advises Max Blankfeld of Family Tree DNA. Still, Family Tree keeps a database where clients with mtDNA matches can contact each other.

In recent years, scientists have discovered unique mtDNA signatures for Native Americans and Europeans, allowing people to either confirm a suspected heritage or gain a historical understanding of their background through books like "The Seven Daughters of Eve" by Bryan Sykes. Mitochondrial DNA tests range from $99 to $500.

Autosomal Testing: The difficulty of Y-DNA and mtDNA testing is that only two lines of ancestry are revealed. If you're a woman, you won't even have a Y chromosome for a Y-DNA test. To find information on other family lines, you need to locate and test relatives who carry the lines you're looking for. If your suspected Native American great-grandmother is on your paternal side, for example, the only way to confirm a Native American mtDNA would be to find a descendant who claims great-grandma as his or her mother's mother's mother. In many cases, that descendant might not even exist.

Science is attempting to solve this through autosomal DNA tests. Autosomal DNA tests examine your non-sex chromosomes to tell you your ethnic make-up (admixture) or ancestral origins by comparing your genetic signatures to other signatures found around the world. Trying to tease out a person's varied heritage from his or her recombined DNA involves complex statistics and comparisons to a database with as many different genetic signatures as possible. This has made autosomal testing one of the newest and most controversial of genealogical DNA tests.

Bennett Greenspan doesn't believe present autosomal DNA tests prove much of anything. "I find it's all dependent on the database you're comparing against it," he said, describing databases over-represented with certain ethnic groups.

Donald Yates of DNA Testing Systems agrees that databases are important, but said a skillful lab is even more important to receive an accurate read-out of your heritage. "Larger databases just mean larger amounts of statistical noise, if all you do is spit out results and hand customers a bunch of numbers and a human migration map," he said. "We have a large body of experience and pride ourselves on evaluating and interpreting results in terms of world history." Autosomal tests range from $150 to $250, with additional ethnicity panels (African, European, Native) costing extra.

Which test is right for you? "All the exciting advances are in the area of autosomal [|markers]]," said Yates. "Y chromosome and mitochondrial testing has gone as far as it can go. People are beginning to realize that these are only two lines out of many." Greenspan, however, said while limited to direct maternal and paternal lines, only Y-DNA and mtDNA can offer trusted results. "These tests are very rock solid," he said.

Which test is right for you depends on what you want to know. Y-DNA testing can help find a most recent common ancestor (MRCA) for different families with your surname, while both Y-DNA and mtDNA can reveal ethnicity and ancestral origins for at least two lines. If the time and cost of testing all your different family lines is too much, an autosomal test may give you some insight into your background, even if it can't determine which ancestor has contributed each part of your results.

Just be aware that this new science, while offering much, still leaves some questions unanswered. Yates lists some questions he's heard from customers: "Can I find out how much Celtic (German, Jewish, Viking, etc.) blood I have? Can I find out which ancestor gave me the arthritis (heart condition, fibromyalgia, etc.) gene? Can I find out where my mother's father (father's mother's father, etc.) came from?"

At this point, said Yates, the answer is no. "All are hopeless as far as science is concerned."

Source Information: GenWeekly, New Providence, NJ, USA: Genealogy Today LLC, 2009.

The views and opinions expressed in this article are those of the author and do not necessarily reflect the views of Genealogy Today LLC.

*Effective May 2010, GenWeekly articles that are more than five years old no longer require a subscription for full access.

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