Genetic Genealogy: A Powerful Tool for the Family Historian

By ⋅ March 22, 2012 ⋅ Post a comment

Hidden within your DNA is the story of your family’s history, a snapshot of your ancestors and their trials and tribulations. Several companies are now helping family historians explore their DNA and unlock this hidden story in order to unravel genealogical mysteries and connect with genetic cousins.

Genetic genealogy testing first became available in 2000 with simple Y chromosome or the mitochondrial DNA tests. Just a few years ago, however, autosomal DNA tests entered the marketplace and thousands of genealogists and genomics enthusiasts have taken these tests to learn more about themselves and their past.

Humans have 23 pairs of chromosomes, including one pair of sex chromosomes (an X and a Y chromosome in males, and two X chromosomes in females). The autosomal DNA is the 22 pair of chromosomes other than the sex chromosomes, which constitutes several billion base pairs. Autosomal DNA tests examine hundreds of thousands of locations throughout these 22 chromosomes, although tests in the not-so-distant future may examine the entire genome.

The results of autosomal DNA testing can be interpreted in several different ways. For example, most companies offer an admixture analysis, which attempts to associate individual segments of the DNA with regions of the world such as Africa, Asia, Europe, and/or the Americas. The results are typically presented as percentages of the test-taker’s DNA which is believed to originate from each region.

The results of autosomal DNA testing are also used to identify genetic cousins. Testing companies will compare the test-taker’s DNA sequence to all other test-takers in the database in order to identify shared segments of DNA. Depending on the number and size of the shared segments, the company can predict a possible relationship between the genetic relatives, ranging from siblings, to grandparents, to 10th cousins.

Another very common use of autosomal testing is to explore adoption. In addition to many adoptees who are using autosomal testing to identify biological relatives, many family historians are using the tests to examine the biological roots of adopted ancestors. I’m using autosomal testing in an attempt to identify the unknown parents of my great-grandmother, Helen Johnson.

Helen Johnson was born on March 3, 1889 in upstate New York to a “Minerva D. Johnson” and unknown father. By the time she was 13, Helen had been adopted by at least three different families. Helen never learned anything about her biological parents, and in the years since her death I haven’t been able to uncover any solid leads using traditional paper records.

Two of Helen’s grandchildren, themselves first cousins, have agreed to undergo autosomal DNA testing and compare their results in order to identify which portions of their genome they share in common. Any DNA that these first cousins share will have been inherited from Helen and her husband. Armed with this information, I hope to identify others that share these portions of DNA with Helen’s grandchildren and are likely to also have descended from Helen’s ancestors. Working back with their family tree I might be able to identify Helen’s mysterious biological ancestors.

My results so far suggest that the system does indeed work. A group of genetic cousins who share a large piece of their DNA with Helen’s grandchildren appear to be related to them through Helen’s husband, Frank. Since I can’t determine which portions of the DNA that the first cousins share came from Helen and which portions came from Frank, I have to use trial and error – and my knowledge of Frank’s family tree – to weed out those genetic cousins that are related through Frank and focus on genetic cousins related through Helen. It’s a challenging process, but likely my only hope of finding Helen’s parents.

Autosomal DNA testing is a powerful new tool for family historians. When a paper trail ends or requires collaborating evidence, these new tests can reveal a wealth of information.

Hear Blaine talking more about how DNA testing works:



Blaine Bettinger edits the Journal of Genetic Genealogy. Read more about him here.

Discussion

4 comments for “Genetic Genealogy: A Powerful Tool for the Family Historian”

  • Christine Raposo

    <3

  • msvnhrn

    I have been a genetic genealogist since 2005, when I began my first DNA project at Family Tree DNA of Houston Texas.  I now manage 8 project for different surnames or families.
    The first thing to consider before actually testing is that you may learn things about your self and your family that you did not necessarily want to know.  You have to decide if you are capable of handling what you find out.
    I have done the Full Mitochondrial Sequence, mtDNA, registered my test result with the National Health Institute’s GenBank, as result, I have my own twig on the mtDNA Phylogenetic Tree complied by Mannis Van Oven.
    My autosomal DNA has been tested at both FTDNA and 23andMe.  Between the two I have about 1100 matches.  A few of which we have been able to identify the common ancestor.
    I also tested at 23andMe for health reasons.  I share this information with my doctors for better management of my health.
    As a woman, I do not have yDNA, but most of the work I do in managing DNA projects concerns analyzing yDNA test results for male project subscribers.  I also encourage my male relatives to be tested in order to confirm family surname lines and identify the oldest known ancestor.  In several instances, I have seen those ancestral lines traced back to Europe.
    For today’s genealogy DNA test is the most accurate and reliable tool for tracing ancestry.

  • http://www.facebook.com/people/Ashley-Cunningham/139300218 Ashley Cunningham

    My husband was adopted with no way of finding out any information about his birth heritage. We had his genome sequenced by 23andme which was a great tool to look up his family history genetically speaking. He now knows more about himself then most do about their own family. It was a great way for him to learn about himself and achieve a better understanding of his own identity. 

  • CeCe Moore

    Very nice summary of a complex subject, Blaine! I’m really glad that you highlighted how useful autosomal DNA testing can be for adoptees since this is a message that I would love to see get more attention.