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Understanding Your Y-DNA Test Results
By Jim Strachan
August 30, 2008

The author of this article, Jim Strachan, is the Group Administrator for the
"Strachan Clan" Y-DNA Project at FamilyTreeDNA.com.  

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In the science of genealogy, Y-DNA is quickly gaining significant recognition in assisting various families to re-connect. 

The accurate spelling of surnames, and public records documenting family genealogy (for example, birth certificates and marriage licenses) are a relative modern invention typically starting in the mid- to late-1800s.  Moreover, in Scotland "irregular" or "runnaway" marriages was a practice of marriage without government license or documentation.  An irregular marriage came about in one of three ways: by mutual agreement, or by a public promise followed by consummation, or by cohabitation and repute.  These irregular marriage registers are not held centrally, and indeed the whereabouts of some is unknown. It has been suggested the rate of unrecorded irregular marriages may be as high as 30 percent. 

This lack of genealogical primary documentation is preventing most families from tracing their heritage and family lineage beyond 150 to 200 years.  To help usurp this proverbial roadblock, genealogist are finding Y-DNA testing to be of significant assistance.

 

Y-DNA testing is widely used in various surname projects, as it tests male DNA.  Obviously, only testing male DNA in a surname project makes sense, as surnames are passed through the male line.  By testing various markers ("Alleles") these projects can help identify lost family lineages. 

There are several advantages to Y-DNA testing in addition to identifying the genealogy profile of your male family line. 

• It may provide clues of where to focus additional traditional documentary genealogical research;

• You may be able to verify that your traditional documentary genealogical work is accurate and scientifically verified; and

• You may be able to obtain clues as to the village of origin in Europe of immigrant ancestors.

• You may identify cousins living in opposite ends of the ocean you did not know you had. 

My DNA Report

At this point, let's assume you've swabbed your cheek, and submitted your
Y-DNA to a surname project... now what?  If you submitted your DNA through FamilyTreedDNA.com, you should be receiving a certificate with a chart that looks similar to the one below....

Sample of a 12-Marker test
 

The "HAPLO" column shows what haplogroup you belong.  A Y-DNA haplogroup is defined as all of the male descendants of the single person. Your haplogroup defines a general population, if you will.  For example, haplogroup R1b1 and its subclades are generally identified with the Picts, an iron age people who inhabited much of Scotland, and migrated 10s of thousands of years ago through Ireland and/or France.  Haplogroup I is associated with the Vikings, who invaded Britain in 900 AD.  Haplogroup J2, is associated with the Romans, who also invaded Britain much earlier in about 90 AD.  Further reading on Haplogroups can be found on http://en.wikipedia.org/wiki/Haplogroups. 

The Alleles, or markers, are provided to the right of your haplogroup, and are used to identify recent family lineages.  After all, not all individuals who belong to haplogroup R1b1, for example, have the same genetic markers.

A good Group Administrator for a Y-DNA Project should be able to confirm within a certain probability that you have family members within a group.  If not, then it's quite easy to calculate the probabilities yourself.

The first step is to calculate the genetic difference.  This is done by simply comparing your alleles with another group members alleles, and calculating a 'genetic distance.'

Genetic Distance Chart
Source: Understanding Genetic Difference
** HIGHLY IMPORTANT TEST IS FROM SAME LAB - READ BELOW **

From the above chart, we add the row "genetic distance" together, and in this example, the genetic distance between these two people equal 3.  Depending on the type of test you obtained, you would determine if these two people are related by clicking the appropriate link below.

12-marker interpretation

25-marker interpretation

37-marker interpretation

 

Finding and Using The Same Lab

If participating in a Y-DNA Project, and your goal is to verify relationships, or discover more about your recent or deep ancestral origins, the size of the database where your results will be is of fundamental importance, as you want your results to be compared to as many others as possible.   If you are of Scottish decent, you may want to check if a surname project is available at familyTreeDNA.com.  It's the largest administrator of Scottish surname projects in the world.

If you are thinking about starting a new Y-DNA group project, it is extremely important to use the same lab for all project members.  Different DNA labs do not test the same alleles markers.  Subsequently, trying to compute the genetic difference of dissimilar alleles markers is virtually impossible.  Thus, making your sample group invalid for the purpose of genealogical study.

Not all labs are created equal.  In choosing a lab, it is important to determine their reputation.  I know it may be hard to believe, but labs and samples get contaminated.  Subsequently, find one with stellar credentials such as an association with a university or a well known research lab, scientist involvement, and leadership in the Genetic Genealogy field.

Determine their test procedures.  Make sure that whomever is testing the DNA sample employs blind testing.  Several labs do not use blind testing.  As such, when an ambiguous result presents itself, the lab technician does not re-test the sample... but instead may simply compare the result to another member of the surname project and guess at the value. 

If from the British Isles, Get the 37-Marker Test

The example provided above was a 12-marker test.  Europe was settled by just a few homogenous peoples, and thus the DNA in Europe is less diverse then any place on the planet.  It is for this reason we highly recommend a 37-marker Y-DNA test.   A 12-marker test may likely receive one or more false-positive results.  Moreover, the more alleles tested, the higher the accuracy of test results.

 

Interpreting Genetic Distance Within Surname Projects