Which DNA test is best for me?

People frequently ask the question: which DNA test should I do? Well the response is simple: The test that is best for you very much depends on the sort of questions that you would like answers to.

Below is a selection of the typical kind of questions that people ask about DNA testing and some brief answers to them. Be sure to explore the links for more information. Hopefully this will help you understand what each type of test can do and that in turn will help you decide which one is best for you.

How many types of DNA test are there?

There are 3 main tests you could do, and you could test one of several members of your family - it depends on what questions you would like answered:

• Y-DNA traces your father’s father’s father’s line
• mtDNA (mito or mitochondrial) traces your mother’s mother’s mother’s line
• and atDNA (autosomal) traces ALL your ancestral lines and gives you your ethnic makeup.

Note that Y-DNA and mtDNA will only give you information about one ancestral line each, whereas atDNA gives you information on all your ancestral lines (but only has a reach of about 300 years, compared to 200,000 years with the other two types of test). You may wish to look at this YouTube video I made explaining the three types of test in more detail and giving examples of their application to genealogy.

Here’s a few examples of questions you might want answers to and the best test to address each one:

How do I find out about my ethnic origins?

• atDNA will tell you roughly what percentage of your DNA is from Europe, Asia, Africa, etc. It will also give you rough estimates on a sub-regional level (e.g. "Central Europe" or "France/Germany") but is unlikely to identify a particular country. Currently this ethnic admixture test (also known as biogeographical analysis) only gives crude estimates and will continue to be refined over time. Still, it makes for a pretty picture which the kids can print out and take to school.
• the general opinion among genetic genealogists is that 23andme gives the best genetic ethnicity estimates, followed by Ancestry, and then FamilyTreeDNA.  None of the tests are accurate enough currently to pinpoint ancestral homelands but they might point you in the right direction. Check out this blog post for more info - Making the best of what's not so good by Judy G Russell, The Legal Genealogist, 22 February 2015.
• both Y-DNA and mtDNA will tell you where that one particular ancestral line originated (eg Western Europe). And because both go back about 200,000 years to Africa, they will also give you the crude migration routes those particular ancestors took. More nice pictures for the kids school projects.

How do I find out more about my surname and where it came from?

• do the Y-DNA test. And test the oldest generation, so that would be your father, uncle, or grandfather. If you are male, your Y-DNA should be exactly the same as your father's Y-DNA and your grandfathers, etc all the way back on the direct male line.
• ... unless there has been an NPE along the way. NPE stands for Non-Paternity Event  or Not the Parent Expected. Common causes are secret adoptions, infidelity within marriage, and illegitimacy. These happen in about 1% of cases per generation.

• Start off with the Y-DNA -37 test from FamilyTreeDNA and be sure to join any relevant surname or haplogroup projects. You can find these by doing a search for your name on the FamilyTreeDNA website and it will give you a selection of relevant projects for you to join.

• After reviewing the results of your Y-DNA-37 test, ask the Admins of projects you have joined for advice on what additional testing might be warranted. This could mean upgrading to 67 or 111 markers, or it could mean doing SNP marker testing. The Project Admins will advise.
• If you want to explore your mother's surname, test her brother. He is the one who inherited the Y-DNA that goes with that surname.
• You can research ANY surname in your family as long as you test the appropriate male cousin who bears that particular surname.

How do I connect with genetic cousins?

• Y-DNA will connect you with genetic cousins with whom you share the same surname.
• mtDNA will connect you with cousins on your mother’s mother’s mother’s line but this is the least useful of all 3 tests - because mtDNA mutates so slowly, even an exact match could mean a common ancestor several thousand years ago (rather than several hundred years ago in the case of Y-DNA).
• atDNA will connect you with about 500-1000 cousins you never knew existed (if you have European ancestry). It gives you the most "bang for your buck". Most of them will be distant cousins, but you may spot a few familiar names in your list of matches. The majority will be unknown cousins who are related to you via unknown ancestors beyond your ancestral Brick Walls, or they will be "false positive matches" (particularly if the amount of DNA they share with you is small). You will have hours of fun (and I mean hours) trying to figure out how they are connected. This test has “Retirement Plan” written all over it. But there are two important questions to address:
• who to test?
• and which company to test with?

Who do I test?

• Anyone. Anyone can do a DNA test. But it’s always a good idea to test the oldest members of the family first, for two reasons:
• they will not always be around
• they have more DNA from particular ancestors than you do
• Your mother for example would be a generation further back than you, and thus she will have twice the number of matches on your maternal side of the family compared to you … because she has twice as much “DNA from the maternal side of the family” - each generation loses 50% of the DNA from that side of the family, because only half of it is passed on from parent to child. So your Dad would only have (roughly) 25% of his DNA from his grandfather, you would have only 12.5%, and your son would have only 6.25%. The percentage inherited from any one specific ancestor roughly halves with each generation.
• Testing yourself and a parent helps you isolate which side of the family your matches are from. So if you tested yourself and your Dad for example, any matches you both share in common have to be from his side of the family; and any matches that you have but he doesn’t, have to be from your mum’s side. Of course you could also test your mum to answer this same question, if she is still with us. 
• FamilyTreeDNA store the DNA samples for 25 years free of charge so this serves as a genetic legacy for future generations - could be important as the science of genetic genealogy progresses (and it has only been around for 15 years or so).

Which company should I test with and how much does it cost?

• there are 3 companies - FamilyTreeDNA, 23andme, and Ancestry.com. Each have their pros and cons.
• Re Y-DNA: if you want to research your surname, then only FamilyTreeDNA offer an infrastructure for surname research. You would have to test with them if you wanted to join the Farrell DNA Project (for example). 23andme will tell you what Y-DNA haplogroup you belong to (useful for knowing your crude migration path out of Africa) but that’s it.
• Re mtDA: only FamilyTreeDNA and 23andme offer this test, but not Ancestry. It is of little use for genealogy. 23andme have it as part of their single test (you get Y-DNA, mtDNA, and atDNA all in one test) and FamilyTreeDNA offer it as a separate test. I would start with the mtDNAplus test because it is cheaper ($69) and may give you all the information you need.
• Re atDNA: whichever company you test with, you should upload your atDNA data to Gedmatch (for free). Anyone can do this and it allows you to compare your data with that of people who have tested with other companies and who have uploaded their data to the Gedmatch website. This allows you to fish in 3 genepools instead of 1 (only partial pools in this instance because not everyone uploads their results to Gedmatch). Also, if you test with Ancestry, you should upload your data to FamilyTreeDNA (for $39) so you are fishing in 2 genepools instead of 1 (complete genepools in this instance).
• 23andme will give you a medical risk assessment as well as a ton of genetic cousins. However the medical component was suspended in the US by the FDA and only partially restored in 2015. You may get a more comprehensive range of medical data if you order the test via their outlets in Canada, the UK, Ireland, & Australia but you would need to ask them about this as the situation is likely to change. Also, you may have to use a friend with a Canadian address (for example) as a middleman if you are ordering from outside the US (Canada in this example).
• 23andme give you all 3 DNA tests (Y, mt, and autosomal) for $199 in the US. It is more expensive than the other companies.
• Ancestry just give you atDNA (no Y or mtDNA), usually for $99 although it can be $79 in their frequent Sales. There is very limited product support, no tools (such as a chromosome browser), and if you want to explore the results further you will need to upload to Gedmatch/FamilyTreeDNA. Also, no further testing is possible. The big advantage of Ancestry is that you can link your DNA results to your family tree and that will potentially allow you to compare your DNA with everyone else on Ancestry who has also done so. And many but not all have family trees ... so it can make finding the common ancestor a lot easier.
• FTDNA (FamilyTreeDNA) store your sample for 25 years. Further testing can be done on the sample whenever you want (e.g. Y-DNA or mtDNA, or any future tests). Their atDNA test (called Family Finder) is $99, Y-DNA is $149 (for 37 markers; $129 via the Farrell project) and mtDNA is $69 ($199 for the FMS full sequence).
• I have tested with all 3 companies. I like FamilyTreeDNA the best and have had most success with them (i.e. my closest matches are on FamilyTreeDNA . My guess is that if you have Irish ancestry you will find most of your close matches on FamilyTreeDNA  If you have US colonial ancestry, you will probably find most of your matches on Ancestry. 
• The cheapest option for atDNA would be to test with Ancestry ($99), then transfer your results for $39 to FamilyTreeDNA, and upload them for free to Gedmatch.
• There are also some other neat websites that offer additional third party functionality that are very useful, DNAgedcom offers some tools and I particularly like Don Worth’s ADSA spreadsheet but historically it has only worked with FamilyTreeDNA results. They are developing it for Ancestry and 23andme.

So which test is best for you? Probably the atDNA test from FamilyTreeDNA or Ancestry if you are interested in general genealogy, or the Y-DNA-37 test from FamilyTreeDNA if you are specifically interested in exploring your Farrell surname.

Maurice Gleeson

Jan 2016