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How to begin with DNA testing

Reader Elizabeth and her half-brother share a mystery parent: a father who was absent from their lives and about whom they know next to nothing.

And when Elizabeth finally found that birth father as an adult, she discovered that the problem of understanding her heritage was bound up in Murphy’s Law1 — he turns out to have been adopted and knew nothing about his origins.

Adult And Child Hand Print“In other words,” Elizabeth writes, “half of me is a complete genealogical mystery. Our father died a few years ago, leaving us with no information on his ethnicity, but many questions! We want to find out anything we can about our father’s lineage, (but) how to proceed so that we may get the fullest picture possible about our father’s heritage and any medical information?”

In this case, DNA testing can help a lot — and may fill in many of the missing gaps in this family’s information.

Let’s start with the great advantage here of having one half-sibling of this pair who is male.

Having a father-son relationship between the mystery parent and one of these half-siblings means being able to test YDNA — the kind of DNA that only men have. It’s contained within the gender-determinative Y chromosome that’s passed down through the generations from father to son to son, so only men can take this test and it provides information on the direct paternal line.2

Doing the YDNA test will provide several pieces of information that may help with this puzzle. The siblings will get:

• Their paternal haplogroup: what broad branch of the human family tree their father’s family came from;3

• Data about deep ancestral origins: where other descendants of their paternal ancestors are present today and about their likely migration paths;4

• The possibility of detecting a likely surname of their biological grandfather — if most or many of the male sibling’s matches all share a surname or set of surname variants; and

• A list of others whose YDNA matches their paternal YDNA, who may be genetic cousins close enough to help answer their questions.

But the YDNA test will only provide information about the siblings’ father’s father’s father’s line. And there are all of those ancestors on their father’s mother’s side as well. How to test for those?

Both siblings should do autosomal DNA testing to get that information. Autosomal DNA, remember, is the DNA in what are called the autosomes, the 22 pairs of chromosomes we all have containing DNA randomly jumbled and passed down equally from our mothers and fathers.5 The test helps us locate cousins because it contains segments from many different ancestors whose DNA, by chance, managed to survive that jumbling process (called recombination).6 It’s the kind of testing done with the Family Finder test at Family Tree DNA, the AncestryDNA test from or the test from 23andMe.

And why should both siblings test? Two reasons. First, because since these half-siblings share only a father and not a mother, anyone who is an autosomal match to both of them is likely to be a relative on their father’s side. There are, of course, exceptions, especially if both of their mothers have colonial ancestry. This process of triangulation — looking at the matches they have in common with each other — is a wonderful tool, because the closer matches that they share should point them swiftly to their father’s side of the family.

The second reason to test them both in that, because of that random jumbling process, even full brothers and sisters don’t have exactly the same autosomal DNA. One might get more DNA from, say, their paternal grandfather than the other will, and the other might get more DNA from their paternal grandmother. So the only way to find as many matches as possible — and to find the very best matches — is to “Test as many people as you can.”7

And, of course, more than just testing both siblings is testing as widely as possible in terms of testing companies and databases. When you’re looking for a cousin needle in the DNA haystack, you don’t want to miss out on a critical match because you tested with company A and your most important match only tested with company B. Using third party database sites like YSearch and Gedmatch can really help spread the word around that you’re looking for matches.

And what about the health information? How to get that?

This is harder now that the FDA has cracked down on 23andMe for providing health data analysis without the necessary approvals.8 So the siblings won’t get any health-related reports from any of the three autosomal testing companies right now. But that doesn’t mean they can’t get some information.

There’s a third-party utility site called Promethease that offers to do fundamentally the same thing that 23andMe was doing: run your raw test data against a known database of possible medical issues and give you an overview of what may be lurking in your genes. You can read more about Promethease at SNPedia, and Roberta Estes of DNA-eXplained has a great overview of the Promethease reporting system on her blog, with a review of her own results.9 Any results from the Promethease test that concern the siblings can then be reviewed with medical professionals and even genetic counselors.

So the plan for this mystery parent:

• Step 1: The male sibling should take the YDNA test. Family Tree DNA is the best in the YDNA business, has the biggest databases and the most active surname projects. For YDNA, realistically, it’s the only game in town.

• Step 2: Both siblings should do autosomal testing and test as broadly in terms of testing companies as possible. The least expensive way to do that right now is to test first with AncestryDNA ($99), transfer the raw data to Family Tree DNA ($69) and then test when funds allow with 23andMe ($99).10

• Step 3: Both siblings should get their results — both YDNA and autosomal DNA — into every database they can to keep the hunt going for paternal-side relatives. That includes sites like YSearch for YDNA and for autosomal DNA.

• Step 4: Both siblings can run their raw data files from the autosomal tests through the Promethease system to get some basic health data, and then follow up if need be with medical professionals.

• Step 5: Last but never ever least, the siblings need to work patiently and thoroughly with all of their matches to develop the paper trail genealogy that will help reveal their father’s side of the family. DNA testing only produces effective results when it’s used with, not instead of, the hard work of doing the basic paper trail analysis.


  1. “Murphy’s law is an adage or epigram that is typically stated as: Anything that can go wrong will go wrong.” Wikipedia (, “Murphy’s law,” rev. 20 Mar 2014.
  2. See ISOGG Wiki (, “Y chromosome DNA tests,” rev. 5 Mar 2014.
  3. See ISOGG Wiki (, “haplogroup,” rev. 4 Mar 2014.
  4. Paternal Lineages,” Family Tree DNA Learning Center ( : accessed 19 Apr 2014).
  5. ISOGG Wiki (, “Autosomal DNA,” rev. 31 Mar 2014.
  6. ISOGG Wiki (, “Recombination,” rev. 1 Feb 2014.
  7. See Judy G. Russell, “Sibling rivalry,” The Legal Genealogist, posted 9 Mar 2014 ( : accessed 19 Apr 2014).
  8. See ibid., “23andMe suspends health tests,” posted 6 Dec 2013.
  9. Roberta Estes, Promethease – Genetic Health Information Alternative, DNAeXplained – Genetic Genealogy, posted 30 Dec 2013 ( : accessed 19 Apr 2014).
  10. See Judy G. Russell, “2014: Most bang for DNA bucks,” The Legal Genealogist, posted 6 Apr 2014 ( : accessed 19 Apr 2014).
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