What DNA Test Should I Take? Part 1: An Introduction To The Three Available Tests.
The most common question I am asked about genealogy or family research is,
“What DNA test should I take?”
This week, I have received a couple of emails from friends and family members asking what test to take. Last week, a friend texted me, “Based on your suggestions, I got DNA tested and the results just came in. My bio dad is supposedly part Native American but my results show no Native ancestry. What happened?” Also just recently, I have encouraged an African American gentleman who shares an ancestral surname with me to get tested so that we can look for shared genetics.
I’m grateful to know that my blog is encouraging people to get tested. You have stories hidden in your genetic ancestry– some exciting; some possibly uncomfortable. But these stories are waiting to be discovered and passed on. Stories of who your people were and where they came from. Stories of what ethnic race your newly found cousins may be (I have a number of African American cousins though I don’t have any African American ancestry), or who your biological father is. This brings up one important rule of DNA testing: Don’t go through the process unless you are ready for whatever the results may expose! DNA doesn’t lie.
The answer to the question can be a bit complicated as the test chosen is dependent on your purposes for testing. As well, each available test works a little differently.
Following is a guide to the available tests and what you can expect from each. After reading, pinpoint what it is that you are attempting to figure out and go from there to select the appropriate test.
Part II of this blog entry will overview strengths and weaknesses of the four primary testing companies. It will post later this week.
So, First, What Is a Genealogical DNA Test?
I call it a chance to spit into a tube and feel either really ridiculous doing so or quite the scientist!
More seriously, a DNA test is a powerful method of examining your genome (your complete set of genetic instructions) at specific locations. Your results are compared to others in the database who have similar lineage and ethnic patterns, then a comprehensive analysis will be run that identifies thousands of genetic markers.
Getting started requires selecting a testing company, choosing a specific test or tests, and placing an order online. Shortly, a kit will arrive in the mail with instructions on what to do. Depending on the test, it may be a cheek swab or it may be a spit test. One forewarning—some elderly persons have a difficult time coming up with the amount of saliva required for a spit test. It’s not much but may be too much for an older relative. For these persons, the cheek swab test may make more sense.
Send your pre-paid package back in, wait several weeks (up to two months depending on backlogs) and—voila—your results will show up in your newly made online account! Then the fun of discovery begins.
What Test to Take?
Currently, there are three genealogical DNA tests available. Each tests a different part of your DNA:
Autosomal Test (atDNA)—for finding matches on all your ancestral lines
Y-Chromosome Test (Y-DNA)—tests the direct paternal line
Mitochondrial DNA Test (mtDNA)—tests the direct maternal line
Autosomal DNA Test:
~ This the most popular of the three tests and the best place for new researchers to begin.
Test examples: The Family Finder test at Family Tree DNA or the AncestryDNA test.
Autosomal DNA is inherited from both parents, so an autosomal test may be taken by either a male or female and can be used to test for relationships in all family lines. This test studies genetic markers found in the 22 chromosome pairs which contain DNA from both of your parents. This DNA has been randomly combined and passed down.
The results from an atDNA test provide you with matches to your genetic cousins for about five or six generations back. These matches are other individuals in the database of the testing company who have also taken the test and have been found to share a common ancestor with you. Depending on the testing company, you will be provided with methods of reaching out to these new cousins, as well as an estimate of how closely related they are to you.
As well, this test provides a detailed geographic breakdown of your ethnic makeup. These admixture percentages are considered reasonably accurate but this is still an evolving science.
Your cousin match results will NOT tell you which branch of your family the match is on—i.e., paternal or maternal side—so you will have to figure that out by getting other family members tested, especially your parents, if possible. Doing so will help narrow down potential matches.
Any autosomal match between you and newly found cousins (shown on your results) indicates a possible genetic connection. Close relatives will share large fragments of DNA from a common ancestor. The more segments you share with someone, and the greater the length of those segments, the more closely related you are.
Also note that no DNA test is able to ‘prove’ that an individual is American Indian and/or Alaska Native, or that the person has ancestry from a specific tribe. Unfortunately, the Native American diaspora is fairly poorly sampled because many indigenous populations refuse to test, making it difficult to adequately detect NA DNA. Read more about proving Native American ancestry at this link: http://dna-explained.com/2012/12/18/proving-native-american-ancestry-using-dna/.
The Family Finder test at Family Tree DNA and the AncestryDNA test costs $99 plus shipping. Discounts can be found occasionally. The company, 23andMe, offers a test for $199, but it includes health information such as carrier status, wellness, and traits reports.
The International Society of Genetic Genealogy provides a detailed comparison chart of the autosomal tests offered by five companies. The chart is available here: http://isogg.org/wiki/Autosomal_DNA_testing_comparison_chart
This test follows your patrilineal ancestral line back through time– your father, paternal grandfather, paternal great-grandfather, etc. As the Y chromosome passes down virtually unchanged from father to son, it can be used to follow the patrilineal surname but this test can only be taken by males.
A Y-DNA test looks at specific markers on the Y-Chromosome of a man’s DNA; these are known as STR markers (Short Tandem Repeat). If you choose to take a Y-DNA test, you will need to choose the number of ySTR markers to be tested. This can range from a minimum of 12 markers to an 111-marker test. The more markers tested the better the refinement of the predicted time frame in which two individuals are related. But, as the number of markers tested increases, so does the price. If you are attempting to determine whether or not you descend from a specific ancestral line or person, you will need to take at least a 37-marker test. However, for the most valuable results a test of at least 67-markers is recommended.
Results will also determine your Y-DNA haplotype, a genetic code that tells you where your paternal ancestors migrated from and to. Some haplogroups are associated with certain ethnic groups. The most common Y-DNA haplogroup among African Americans is E3a. That most closely associated with Native American populations is the Y-DNA haplogroup Q3.
The best use of a Y-DNA test, if possible, is to create a planned comparison of two persons: have two men who are believed to have the same direct paternal ancestor tested. If the results show that they are a close match, then the DNA evidence is supporting your paper trail.
Once you have your results, you will be provided the opportunity to join a Surname Project. These groups bring together persons who have the same surname or those who belong to the same certain ethnic group or geographic areas and help determine how they are related to each other. Many Surname Projects provide a discount on the cost of future DNA tests if you order direct through them.
Y-DNA tests at Family Tree DNA start at $169 for the 37-marker test and go up to $359 for the 11-marker test.
Mitochondrial DNA Test:
Mitochondria are free-floating structures within cells that convert the energy from food into a form that cells can use. They are the powerhouses of the cell and possess a small amount of their own DNA. In humans, mitochondrial DNA is inherited solely from the mother, enabling researchers to trace maternal lineage far back in time. It is passed down from mothers to both their sons and daughters, but sons cannot pass along their mothers’ mtDNA to their children. All children from the same mother will have the same mitochondrial DNA. The mtDNA test is only useful to females, or for a male testing his mother’s lineage.
Mitochondrial DNA is nonrecombinant, so it passes down virtually unchanged from a mother to her children. As well, it evolves fairly slowly compared to other genetic markers- allowing you to trace your deep maternal ancestry. However, it is generally not used to determine relationships closer in time. If two people have an exact match in their mtDNA, then there is a very good chance they share a common maternal ancestor, but it can often be hard to determine if this is a recent ancestor or one who lived hundreds or even thousands of years ago. Consider it more of an anthropological test versus a genealogical test. Results will show not only the origin of maternal ancestors, but will also show with whom you are related in your maternal line.
The mtDNA test will also provide your mtDNA haplogroup—where your ancient ancestors originated and traveled from. This will provide clues to the ethnicity of your maternal line.
There are several differing levels of mtDNA testing available. These are: mtDNA (HVR1), mtDNAPlus (HVR1 & 2), and mtDNA Full Genomic Sequence. For more information on these, the Family Tree DNA Learning Center can help.
To have your entire genome tested, it will cost $199 at Family Tree DNA.
Later this week: Part II — An Introduction To The Primary DNA Testing Companies.