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What test to take

It’s a question that packs an emotional punch, no matter how many times The Legal Genealogist hears it.

And it came up again yesterday from reader Katie.

“Which DNA test do you recommend,” she asked, “if I’m trying to find out who my father is?”

Few of us who grew up in nominally intact homes can honestly say our relationships with our fathers were unconflicted. Some of us who grew up in dysfunctional or broken homes may actually dislike the man who fathered us.

But nobody who grew up knowing something about the person whose name gets entered in the first box on the paternal side of a family tree chart can really understand the power of Katie’s question.

It’s so much more than “who is he?” It’s also “who am I?”

And in Katie’s case, as a single woman wanting to know about her father, there’s only one possible answer: Katie needs to do autosomal testing — and to test as widely and spread her results as broadly as she can.

First off, why autosomal testing?

That’s because of the way the different types of DNA that we use for genetic genealogy — YDNA, mitochondrial DNA and autosomal DNA — are inherited.

YDNA is the kind of DNA found in the male gender-determinative Y chromosome that only men have.1 It gets passed from a man only to his sons and from his sons only to his grandsons and from his grandsons only to his great grandsons, with few changes down the generations.2 So the line of descent looks like this:


You can see the problem, right? For Katie — a female — the line of descent isn’t going to work. For her, the picture looks like this:


So YDNA testing won’t help when a single woman tries to find her father’s line. It works if she has a known paternal brother or uncle or male cousin. But not when the only person she knows who’s related to her father is herself.

Mitochondrial DNA — mtDNA — is a kind of DNA we all have that serve as energy producers for the cells in our bodies.3 It gets passed from a mother to all of her children — male and female — but only her daughters can pass it on to her grandchildren.4 So the line of descent for Katie looks like this:


And you can see the problem there, too, right? Katie’s not looking for information about those women in red. She’s looking for this guy:


So mtDNA testing isn’t going to help either.

This all leads to autosomal testing. All human beings have 23 pairs of chromosomes — 22 numbered pairs and one gender-determinative pair. The autosomes are those 22 numbered pairs.5 And we get exactly half of our autosomal DNA from our fathers and half from our mothers6 in a pattern that looks like this:


So which test Katie take is a no-brainer. The autosomal DNA test.

The best part about autosomal DNA testing is that almost all of our cousins, out to the fourth or fifth cousin level and sometimes even beyond, are going to share some part of that DNA with us. So anyone who matches us in an autosomal DNA test might be able to provide clues to a missing parent (or grandparent or great grandparent) once we do the hard traditional-genealogy-paper-trail work of figuring out where our common ancestral line is with that match. Even when we don’t know anything about part of our own ancestry, as in Katie’s case, finding matches can help us narrow it down.

If Katie’s mother, or a close relative on her mother’s side, will test at the same time, that will help Katie narrow down her results to her father’s side — anyone who matches her and her mother’s-side relative can pretty much be excluded as a link to her missing father. But those who match her most closely and do not match her mother’s side… oh yeah… those are the matches to focus on. Those are the folks most likely to be her relatives on her father’s side.

So… who to test with? Right now, there are three major companies that offer autosomal DNA testing for genetic genealogy: 23andMe; AncestryDNA; and Family Tree DNA. And Katie needs to test with all three. And use every third party tool available to get her results out there, like

Why? Because most people who do DNA testing will test with only one of those companies. And Katie has no way of knowing who might have tested already and who might test in the future who might be the key to finding her father’s identity — and no way of knowing which company that key match might choose.

My advice on how to do that for the least amount of money stays the same as it’s been:7 test with AncestryDNA first (the usual price is $99; a sale is on right now that drops the price to $79); then when you get the results, take that raw data from AncestryDNA and upload it to Family Tree DNA (the transfer price is $39 (corrected!); free if you can get four others to transfer their results); and then test with 23andMe ($99 for the test there).

That gets you into all of the company databases for the lowest possible price — and you can take the raw data and upload it to GedMatch and any other future third-party tools website that allows you to compare your data to the data of others.

Bottom line: finding fathers means autosomal testing for females (add in YDNA testing for males), and spreading the results out as far and wide as you can.


  1. ISOGG Wiki (, “Y chromosome,” rev. 23 Apr 2014.
  2. Ibid., “Y chromosome DNA tests,” rev. 27 Nov 2014.
  3. What is mitochondrial DNA?,” Genetics Home Reference Handbook, National Library of Medicine, US Department of Health ( : accessed 29 Nov 2014).
  4. ISOGG Wiki (, “Mitochondrial DNA tests,” rev. 9 July 2014.
  5. Definitions: Autosome,” Human Genome Project Information ( : accessed 29 Nov 2014).
  6. See Judy G. Russell, “Autosomal DNA testing,” National Genealogical Society Magazine, October-December 2011, 38-43.
  7. See Judy G. Russell, “2014: Most bang for DNA bucks,” The Legal Genealogist, posted 6 Apr 2014 ( : accessed 29 Nov 2014).
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