Henderson DNA Project – What Level Test Should I Choose?

By James E. Henderson, Project Administrator

A decade ago the big excitement in genealogy was the advent of the public Internet and the ability to use it to correspond with other genealogists. Today, the latest tool in the genealogist’s toolbox is DNA testing. At first, people were intimidated by the science of DNA testing and reluctant to jump into the pool. That’s why the Henderson DNA project focuses on real world applications, staying away from the academic side of genetics that often leaves genealogists more bewildered than informed.

This does not mean we have removed all the roadblocks. One of the most common obstacles facing our prospective members is the question, “What level test should I choose?” The purpose of this update article is to answer that question or at least provide some useful information to help you make the right decision.

The holy grail of DNA testing is the perfect DNA match with a Henderson cousin you did not know you had. A single DNA signature is of no value to the genealogist other than to identify the barbarian people and geographic location where his DNA was first identified. More often than not, our project participants submit their DNA test hoping for the best, hoping our search process will find their perfect DNA match. Joining the Henderson DNA Project is the most important step in that process. Unless you throw your hook in the water, you’ll never catch a fish or in our case, you’ll never find your match.

In the scientific pursuit of your perfect match, our host facility lab, FamilyTreeDNA (FTDNA), provides four different panels or suites of markers for testing which together add up to a total of 67 markers. (Marker—That’s a specific place on the human chromosome, the inheritance of which can be followed from one generation to the next.) These four panels or tests should be viewed as progressive steps. First there is the original 12-marker test, now named the Y-DNA 12 Paternal Line Test. It is also the lowest-resolution test. You can add a second panel of 13 markers. Combined with the first panel, this yields a 25-marker signature (set of 25 numbers). The 25-marker test is known as the medium resolution test. Then, there is a third panel of 12 markers which, when combined with the first two panels, yields a 37-marker signature (set of 37 numbers). The fourth panel adds another 30 markers to produce the 67-marker signature, which is the highest-resolution test.

These different panels do their work by looking at the average mutation rate of certain markers. The average mutation rate of the markers in the first panel is slower than that of the average mutation rate in the second panel. And the second panel average mutation rate is slower than the average mutation rate for the third panel. In fact the third panel average mutation rate is almost twice as fast on average as the first panel. The same logic follows to the fourth panel.

Fast moving mutations allow us to identify different family lines in the total universe of Hendersons. If markers did not mutate or change, we would all have the same DNA signature. For this reason, the highest-resolution test (the 67-Marker Test) provides the best information available on our Most Recent Common Ancestor (MRCA). The low-resolution test provides good information but our MRCA remains a bit fuzzy so it is less useful.

With this information in mind, let’s interpret the results of a typical 67- marker signature:

The first 12 numbers places us in a very large group of very distantly related family lines identified as a single Haplogroup of the human species. From the first 12 numbers of my own DNA signature, FTDNA tells me that I belong to a Haplogroup named “I1a” which is Nordic/Anglo/Saxon in origin. Many of our Hendersons are in the Haplogroup “R1b”, which is Western European in origin. The majority of Hendersons in our DNA project fall into these two Haplogroups.

My Haplogroup assignment of I1a narrows down the pool of family lines from billions to many millions. And my specific sequence of numbers narrows down the portion of the total population to an even smaller segment based on how close the sets of numbers of other lines are to my signature. Thus my specific 12-marker signature brings the population pool down from millions to a few hundreds of thousands.

That’s good news, but here’s the bad news—the exact 12-marker signature I possess is also the exact signature of about a thousand other males who live in Europe, Australia, United Kingdom, Canada, and the United States. These exact matches probably do not share my surname but are still related to me from a time prior to the adoption of surnames, i.e., about 700 years ago in Scotland.

The point is, having an exact 12-marker match or even a nearly exact 12-marker match with another person is not all by itself good enough to be certain you have found your true family line. However, if that person shares your surname then the picture changes. You most likely have found a 13th century relationship, giving cause to add more markers to your test to see if that relationship continues into more modern times. Having found a new Henderson cousin at the12-marker level, I move to the 25-marker test to narrow down the pool of other male lines that possibly could be related to me. Even then, I will have many matches with people of different surnames. When I receive the full list of perfect matches at the 25-marker level, I will sift through the nonHendersons and look only at the Hendersons who survived the refined testing.
It is with these Hendersons that I will begin a serious exchange of information.

In a cooperative effort with my new Henderson cousins, I move to the next panel of test results that will take the probability of our relationship to a higher level since it is more likely that people who share an exact 37/37 match are more recently related than those who only share a 25 marker match. And of course if you then add in the surname filter combined with the 37-markers, you move closer to your true family line.

Okay, this has already become a little complicated so let’s summarize. We know that a 12-marker test will place us in a group of about a million people who had the same Iron Age barbarian father. If we find a Henderson match, based on the 12-marker test, we know, with a 90% probability, this newfound cousin shared a common male ancestor in or around the 13th century, most likely in Scotland. If our new Henderson cousin agrees to take our test to the next panel and we remain a perfect match, we can conclude that we shared a common ancestor in or around the 18th century. Up the ante to the next panel where a perfect match tells us we shared a common ancestor in or around the 19th century. At this point, the excitement is too much to handle so we take the final leap to the fourth panel and find that our perfect match predicts, with 90% probability, a common ancestor sometime after the year 1900. By this time, we should be exchanging all of our traditional research records in an attempt to determine who that common ancestor might have been.

If at any point in this process we have less than a perfect match with our Henderson cousin on any of these panels, we need to rethink our strategy. If we have a mismatch by one or two or even three numbers, it’s still possible we are related. The point being, as mismatched numbers go up, the probability of a true family relationship goes down.

Okay, back to the question, “Which test should I take?” My conclusion is you should take the lowest, most inexpensive marker test (12-Marker) offered by FTDNA, unless you already have a suspected cousin with whom you want to compare results. In that case, start at the highest marker test you both can comfortably afford. I call this the “go slow” approach. Find a perfect DNA match with another Henderson, then work with that new cousin before you both decide to move to a higher level test.

If cost is an obstacle, try the family approach. Ask family members who are interested in their genealogy to work together. Identify one male who will submit the DNA sample and share results with the entire family. This is good logic because brothers share the same DNA signature as their father. Their father shares the same DNA signature with his own brothers and all the sons of those brothers. It would be a waste of scarce money for all these men to submit samples for testing individually because they already know they are closely related.

There is no price penalty for starting low and refine to a higher level test later. Likewise, there is no discount for jumping right into the 67-marker test. It all comes out to be about the same cost in the long run whether you start with 12-marker test and gradually go to 67 or just start out with the 67-marker test. The difference lies in the value of the new knowledge you receive and the significance of that new knowledge on your genealogy.

For more information on DNA Testing, go to:  www.dna-testing.advisor.com

This article was originally published in the An Canach, Summer 2007.  The An Canach is the newsletter regularly published by the Clan Henderson Society for members.