The following excellent explanation of the DNA
options come from the DNA Newsletter Facts & Genes from Family
Tree DNA July 24, 2002 Volume 1, Issue 1. The Clan, at the instigation of
the Mac Aodhagáin, is now running a Surname Project
as recommended in this article.
What will Genetic Genealogy do for your research?
The term Genetic Genealogy refers to the application of science, through
testing DNA, to uncover information about your ancestors. There are currently
two types of tests available to the general public: the Y-DNA test and the mtDNA
test. The Y-DNA test tells you about your male ancestors, and the mtDNA test
tells you about your female ancestors.
The Y-DNA test is for males only as it tests the Y chromosome, which is
only found in males and is inherited from the fathers direct paternal
line (grandfather to father to son). Scientists have determined that the Y chromosome
is passed from father to son unchanged, except for random mutations that are
estimated to take place only once per 500 generations per marker.
The direct line of descent for males is critical. Events such as adoption
or an extramarital male birth would break this chain. All males with a direct
line of descent from your most distant known male ancestor should have the same
Y chromosomal pattern, or genetic fingerprint, except for the random mutations.
If you compare the genetic fingerprints of these male descendents today, they
How can this help you in your research? Testing the Y chromosome can verify
what is known. It can point you in a direction for further research, or prove
or disprove a relationship or theory. Family Tree DNAs Y-DNA test can
find others to whom you are related. It might point you to a specific geographic
location for further research. The individual reasons for doing Y-DNA testing
vary significantly, from curiosity to specific genealogical research goals to
large surname projects.
Here are just a few examples of the use of Y-DNA testing. For example, suppose
two immigrants, who came to the U.S. in 1740, had the same surname, but you
can't connect them. By testing direct male descendents of each immigrant, you
can determine whether or not the two immigrants were related. In another situation,
your family legend is that your surname was changed on immigration. All persons
with the new surname found in the US fit into your tree. Your grandfather gave
you two possible original surnames. By testing descendents of the two possible
original surnames, you could determine if you were related to either. In another
example, you have found your surname in New Zealand, and those people come from
the same County in Ireland. By testing both groups, you can determine if they
are related, and perhaps you will focus more research in this Irish county for
paper records. In many cases, you may only need as few as two participants to
apply Y-DNA testing to solving your genealogy brick walls or adding more information
to your family
Y-DNA Surname Projects attempt to test all lines, branches and variants
of a particular surname to determine which are related. Surname Projects can
start small with a subset of the surname and be expanded in phases.
The mtDNA test is available for females and for the female ancestors of
males. We all carry mtDNA inherited from our mothers. Anthropologists have determined
that there exist approximately 20 daughters who are descended from a single
mitochondrial Eve. Family Tree DNAs mtDNA tests will determine
from which daughter of Eve you descend. You can then use the Family Tree DNA
database to find others whom you match
How many markers should I test?
The question asked the most often by people considering the Y-DNA test is How
many markers are enough?
The place to start is to define the term marker. A marker is a location
on the Y chromosome that may be tested for Genetic Genealogy. These locations,
or markers, have names, such as DYS #19 or DYS #385a or DYS #439. When a marker
is tested, the result is reduced to a number, which represents the number of repeated
patterns of the DNA protein sequence at a specific location on the Y chromosome.
Family Tree DNA offers a 12 marker Y-DNA test and a 25 marker Y-DNA (called Y-DNA
Plus) test ( a 37 marker test is now available). The difference is that the Y-DNA
Plus test results, with its additional markers, reduces the time frame to the
Most Recent Common Ancestor, or MRCA. For both tests, the number of markers that
match can determine whether you and another participant share a common ancestor
and how many generations ago that common ancestor might
If two individual's test results match exactly (12/12) in the 12 marker test,
there is a 99% probability that they are related. The issue then becomes: when
did this common ancestor live? Unfortunately, science cannot pinpoint the exact
generation, but science can provide a range of time when the common ancestor might
If two individuals match in the 12 marker test for either 10 out of 12 (10/12)
or 11 out of 12 (11/12), they are also considered related, but the time frame
to the common ancestor, MRCA, is more distant than if they had a 12/12 match.
Where the matches are less that 10/12, the two individuals are not considered
to be related.
If your 12 marker test results match another participants exactly, 12/12,
your common ancestor occurred between 1 and 62 generations ago, with a 50% probability
that the common ancestor lived 14.5 generations ago or less. There is a 90% probability
it was within 48 generations and a 95% probability it was within 62.
You can shorten this time span by increasing the 12 marker test to a 25 or more
If two individuals match exactly (25/25) in the 25 marker test, their MRCA would
have lived between 1 and 32 generations ago, with a 50% probability that the common
ancestor lived 7 generations ago or less. There is a 90% probability the MRCA
was within 24 generations and a 95% probability that it was within 32 generations.
Therefore, increasing the markers tested from 12 to 25 lowers the time frame to
the MRCA from 14.5 to 7 generations.
Clients can choose either the 12 marker test or the 25 marker test, depending
on their objectives. A 12 marker test can be upgraded to a 25 marker test at a
later date. The Lab used by Family Tree DNA, based at the University of Arizona
in Tucson, keeps a sample of your DNA stored under a kit number. If, later in
your project, you decide to expand your test to 25 markers, the additional markers
can easily be tested from the DNA already stored for reprocessing
Many clients struggle with the choice between 12 and 25 markers, as wellas who
to test. Our recommendations vary based on the client's objectives and situation.
Examples are provided below to assist you in making your decision for the number
of markers and selecting participants.
There is only one surviving direct male descendent in your line, traced back to
the early 1800's with documented research. You are not ready to start a project
and haven't researched other lines with your surname. You never find the time
to spend to understand DNA testing. Your direct male descendent is in his late
On the surface, it appears that you have plenty of time to learn about DNA testing,
and have your relative tested. Unfortunately, once this direct male descendent
is gone -- you can probably never get a DNA sample. In the situation where there
is only one surviving direct male descendent, regardless of their age, we recommend
Either the 12 or 25 marker test will do. Any time in the future, others with your
surname can be approached to be tested for comparison. The objective today is
to get a sample from your relative and have it tested to ensure that you will
not be denied the opportunity in the future. You will then have the results for
the direct male descendent, the results will be stored in our database, and the
sample will be stored for your future use.
If there are as few as three direct male descendents in your tree, we recommend
immediate testing of two of the males. The reason to select two is to confirm
that there were no adoptions or extramarital male births. Often, it is only a
priority to test males if they are elderly. The issue is not age. If the person
is gone, for all practical purposes, their DNA is gone. We were able to assist
a client late last year, whose only direct male descendent was killed in a car
accident. Securing the sample took tremendous effort, and the involvement of the
spouse for approval and the medical examiner for a sample. It was sheer luck that
the client remembered in such a stressful situation, and contacted Family Tree
DNA on a Saturday night at midnight, so that we could immediately overnight a
In summary, if you have a small number of direct male descendents in your line,
we recommend immediate testing of two participants, to confirm a match and to
have the sample and results stored for future reference. If you do not get an
exact match, expand the testing to any remaining direct male descendents to determine
where and when a non-paternity event occurred, such as adoption.
Two immigrants came to the U.S. in 1740 with the same surname. Extensive research
has occurred, but you can't connect them with paper records. There are many descendents
today in the U.S.
Our recommendation is to test two direct male descendents from each immigrant's
line for 12 markers. The rational behind this recommendation is that there is
large span of years between the immigrants arrival and today, as well
as many birth events that provide an opportunity for an extramarital male birth
or an adoption. By selecting two males from each line, you would expect a match
within each line to validate the results. Then, when you compare the results
from the two lines to each other, you would be confident that you have accurate
You are interested in determining which lines with your surname are related.
Your surname can be found in England, Ireland and the U.S. You have extensive
paper documentation on your line and contact with one researcher in England
who has researched their line. This other researcher has also identified nine
separate trees with this surname.
Where and how do you start?
You are an excellent candidate for a Surname Project.
A Surname Project can be established with a minimum of six participants. There
are two primary approaches, depending on the size of your Surname
Project and the extent of the paper genealogy records. For a relatively
rare surname, with limited descendents and excellent genealogy records, we recommend
testing one or two direct male descendents from each line for 12 markers.
If matches occur, you may want to expand to 25 markers. When no match occurs
between two the lines, we recommend that an additional direct male descendent
be tested in each of those non-matching lines.
For surnames that are not rare and have many branches and descendents, we
recommend testing two males from each line to establish the genetic fingerprint.
(Remember: In every generation, the opportunity for an extramarital male birth
or adoption exists). Where no match occurs, expand the testing in the two lines
that do not match to include an additional male in each line.
In conclusion, the situations and objectives vary between families. The examples
provided above may help you determine what approach to take with your DNA testing.
If you are not sure of your objectives, and want to
get started, our recommendation to clients is to select the 12 marker test,
and to later upgrade to the 25 marker test when a match occurs, to reduce the
time frame for the common ancestor, MRCA.
Citation: Copyright 2002, Family Tree DNA "Facts & Genes"
Clan Egan DNA Project
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