DNA Testing for Genealogy – Getting Started, Part One

Posted July 18, 2012 by Geni | 35 Comments

We’re excited to bring to you a special guest blog post by genetic genealogist CeCe Moore. Some of you may recognize her from her blog YourGeneticGenealogist.com. For the next few weeks, she’ll be providing a great overview about DNA testing for genealogy. So without further ado, here’s part 1! Enjoy!

Interest in DNA testing for genealogy has reached an all-time high thanks to its increasing sophistication and the resulting visibility in the media. We hear about what we can learn from DNA testing from popular genealogy television programs, news stories and in advertising.  As a result, many family history enthusiasts have expressed their desire to venture into the fascinating world of genetic genealogy, but don’t know where to start.  If you are one of these people, then I am writing this for you. In a series of four posts over the next month, I will explain the three different types of DNA testing currently used by genealogists to discover more about their family trees. I will endeavor to help you determine which test or combination of tests would be best suited to your interests.

The first step is to determine your testing goals.  Do you have a general curiosity about genetic genealogy or is your focus more specific? For example, please consider the following questions:

  • Are you primarily interested in researching your surname?
  • Are there specific brick walls that you wish to target with the use of DNA testing?
  • How far back in your family tree are these brick walls?
  • What is the ancestral pattern back to these brick walls, i.e.- mother’s mother’s    mother or father’s mother’s mother’s father?
  • Are you ready for a long-term project or do you desire quick answers?
  • Are there adoptions in your family tree that you would like to explore?
  • Is your primary interest receiving a percentage breakdown of your overall ancestral origins or “ethnicity”?

Currently, there are tests geared at isolating three different types of DNA that can address these questions and others. They are Y chromosome DNA (Y-DNA), mitochondrial DNA (mtDNA) and autosomal DNA (atDNA).  Y-DNA has been in use the longest and, as a result, has the best track record for helping genealogists demolish those proverbial brick walls, so let’s talk about that one first.

Focused on your surname?

Y-DNA refers to the DNA found on the Y chromosome. Only males inherit the Y chromosome, so this test can only be used to trace the direct paternal line.  Simply speaking, a man inherits his Y chromosome from his father who inherited it from his father who inherited it from his father and so on. Testing of Y-DNA can reveal the ancient origins of a person’s direct paternal line. It can also be of great genealogical value since the Y-DNA traditionally follows the same inheritance pattern as surnames. As the surname is passed down from father to son, so is the Y-DNA. Because of this, a male can often identify which direct paternal ancestral line he belongs to by matching with others of the same or similar surnames. For those with ancestral roots in societies with traditional surname inheritance, this type of testing can sometimes help identify common ancestors from several hundred years ago. Though far from guaranteed, an adoptee may even find success in discovering his biological surname by testing his Y-DNA.

If you are a woman who is interested in discovering more about your maiden surname, then you will need to locate a male of that surname from your family. You can test, for example, your father or brother (full or paternal half), a paternal uncle or a paternal male first cousin. If needed, you can even test a more distant cousin as long as he carries the surname of interest and shares a common ancestor along your direct paternal line.  Remember, you cannot test your son for this purpose, since he carries the Y-DNA of his father!

Although this test is limited in scope, it can be used in ways not immediately obvious. For instance, you can identify any specific surname of interest in your family tree, follow that surname down the branches toward present day and use these same rules to try to locate an appropriate male for testing.  This way, the usefulness of Y-DNA testing in your family research can be expanded beyond this one ancestral line.

Perhaps the best news about Y-DNA testing is that there are thousands of surname-specific DNA projects headed by volunteer genetic genealogists to help you with your DNA research. With the birth of the first commercial genealogy DNA testing company, Family Tree DNA, in 2000, surname projects immediately began springing up. Some have already had great success in determining the origin(s) and family branching of their particular surname of focus, while others are still searching for enough participants to reach solid conclusions.  You can participate and assist in focused research on your surname by joining the appropriate project. To locate your surname project, you can try Googling  “(Insert surname) + DNA Project”. If you find that one does not exist, you may want to consider starting your own and recruiting those genealogical cousins that many of us are already in contact with through our family history research.

As in all genealogy, I do want to point out that immediate gratification is not guaranteed. Some participants have not yet found success with this type of testing due to the lack of matches to their DNA in the databases. However, time should rectify this problem for most with the growing popularity of testing and the increasing numbers of those contributing their DNA to this research. For cultures that did not utilize inherited surnames in the traditional way, Y-DNA testing will not be as effective, but can still be useful in identifying probable origins and migration patterns.

The Y-DNA tests on the market currently offer anywhere from 12 markers to over 100 markers. I suggest testing at least 37 markers to start with (around $150). In the simplest of terms, “markers” are specific spots on the Y chromosome for which numerical values are assigned based on each individual’s DNA signature. So, for example, if you order a 37 marker Y-DNA test, this means you will generally receive a string of 37 numerical values. A man’s closest matches may be found by comparing his string of numbers to all of the other results in the company’s DNA database.  As a general rule, the men who have the most markers that match each other are the most closely related to each other.  The approximate number of generations back in time that two men shared a common paternal ancestor is estimated by determining how closely the individual strings of numbers match each other.  (Don’t worry; the testing company will automate these calculations for you.)

Since this test exclusively addresses your direct paternal line, remember the results are only informative of a very small portion of your family tree. If you are interested in a more general overview of your ancestry, please check back for my post in two weeks on autosomal DNA tests.

Next week, we will take a look at mitochondrial DNA testing. (Update: Read part 2 here).

CeCe Moore is a professional genetic genealogist and writes the popular blog Your Genetic Genealogist, She is the administrator of several surname DNA projects and the ISOGG DNA Newbie Yahoo Group. CeCe serves as an “Ancestry Ambassador” to 23andMe, on the Advisory Board of the Mixed Roots Foundation and is a member of Mensa. Her favorite genetic experiment is her seven-year old son, Nicolas.