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Ancestry Daily News
1/30/2003 - Archive
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DNA Testing: Why Markers Matter |
DNA Testing: Why Markers Matter
About a decade ago, the Internet started to revolutionize the genealogical world
by making it exponentially easier to locate useful resources and distant cousins.
Now DNA testing is ushering in the next revolution by supplementing traditional
research with a technique that can sometimes help even when the paper trail
runs out.
If you're like many of us, you've played with the idea, but haven't made the
leap of purchasing that first test kit. Being a rather impatient person, I made
my first foray into this new territory slightly about two years ago and would
like to share some observations from the perspective of someone who has at least
a tad of experience.
When first getting started, there are several issues that merit consideration,
not the least of which are what you hope to accomplish through your testing
and which test you should order. Although DNA testing can be used to assist
with the unraveling of a variety of genealogical situations, it is currently
used mostly for surname or common ancestor testing. Simply put, this is when
people of the same surname are tested to learn more of their origins, usually
with the hope of confirming that they do indeed share a common ancestor. I hoped
to do this, for instance, when I had four lines of Smolenyaks hailing from the
same village examined.
For ordering purposes, this is generally referred to as Y chromosome or paternal
ancestry testing by those who offer these services. Because this is the prevalent
emphasis in current testing, I will leave it for another article to explore
other possibilities, and focus for now on which test to order.
The Cost Factor
Virtually everyone who launches a DNA study will have more than one sample tested
(frequently, a lot more), so price is a serious factor. Not surprisingly, this
is what most of us zero in on when making our first order.
Fortunately, as with all technologies, competition has sparked a gradual lowering
of prices coupled with an improvement in services provided, but the cost is
still more than one typically pays for genealogical indulgences. Although it's
difficult to make direct comparisons because of variations in test features
and bundling, you can expect to pay roughly $99 to $245 for a single Y chromosome
test.
Multiply this cost by the number of tests you expect to have done and you can
see this is not a trivial decision. Still, with the benefit of a little hindsight,
I have reached the conclusion that there's at least one factor that's more important
than price.
Markers
When you receive your test results, you are given a report with your Y-DNA alleles,
a series of numbers each indicating how many times a particular pattern repeats
itself at a specific location—or marker—on a chromosome. Each marker,
then, is reported as a number and it is this series of numbers that is used
to differentiate among samples, or in some happy cases, to find matches.
For surname projects, the numbers themselves are not as important as how they
compare with others who were tested in your study. Ideally, you'll want to find
a perfect match to confirm common ancestry.
The Match Factor
When these tests first came to market, the results showed only four to ten markers.
While it is still possible to purchase tests of ten markers, you now have the
option of being tested for as many as 25 markers. When I first began my own
study, I didn't fully appreciate why I should opt for as many markers as possible,
but now I understand that more markers translate into fewer matches and more
genealogically useful results.
Why would you want fewer matches? My husband's experience will shed some light
on this. When we compared his initial 12-marker results to the others in our
surname study, we were rather stunned to find no matches (Surprise, all Smolenyaks
are not related!) -- so our next thought was to look beyond our community. When
we did, we learned that he is genetically generic and had 35 perfect matches
and another 356 close matches (i.e., one- and two-step mutations) in a database
of only 6,400 samples. These 391 exact and near matches weren't all that helpful
since it suggested that he could share common ancestry with perhaps one in 20
people.
When we had him retested for 25 markers, however, he had only one perfect match
and a pair of two-step mutations in this same database. From a genealogical
perspective, I'm not very interested in the 391 close matches from the 12-marker
test, but I'm curious to know more about the three people whose results fit
so snugly with his 25-marker results.
The Time Factor
In addition to producing fewer matches, testing for more markers makes the results
more meaningful. When you are fortunate enough to find a match, the first question
that naturally springs to mind is how far back that common ancestor of yours
might have been. Is your link five generations ago, fifteen or fifty? There
is no precise way to answer this question, but results can be presented in terms
of probabilities.
For example, a 12 for 12 match tells you that there is a 90 percent probability
that your common ancestor lived within the last 48 generations and a 50 percent
probability that he lived within the last 15 generations. A 25 for 25 match
narrows these time frames, revealing a 90 percent probability that your common
ancestor lived within the last 20 generations and a 50 percent probability that
he lived within the last seven generations. Additional markers clearly go a
long way to bringing test results into genealogically relevant time spans!
More Markers, More Meaning
I like to refer to the merger of genetics and genealogy by my own fabricated,
hybrid word of "genetealogy." For those of you who might be thinking
of taking your first steps in genetealogy, I urge you to consider not only the
immediate bottom line, but also what you'll ultimately be able to learn from
your results, even if they don't produce the hoped-for matches. An additional
investment now might save you a lot of retesting or upgrading (and consequently,
money) down the road!
Megan Smolenyak Smolenyak, author of Honoring Our Ancestors: Inspiring
Stories of the Quest for Our Roots, will be writing more on genetealogy and
would like to know what questions readers would most like to have answered regarding
this topic. What aspect confuses you the most? What do you want to know before
starting your own testing? Please send your comments through
at: Megan's website
Megan will be at the following events:
Carpatho-Rusyn Society
February 23, 2003, Annandale, VA
Half-day event with talks including "Jump-Starting Your Eastern European
Research" and "Building a Village-Based Community."
Ohio Genealogical Society 2003 Conference
Ohio: 200 Years of Heritage
April 25-26, 2003, Columbus, OH
25th—"Honoring Our Ancestors" 11:30 (luncheon)
26th—"Jump-Starting Your Eastern European Research" 2:30-3:30
Copyright 2003, MyFamily.com Inc.
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