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Ancestry Daily News
6/3/2003 - Archive
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DNA Testing for Genealogical Purposes: A Basic Introduction |
DNA Testing for Genealogical Purposes: A Basic Introduction
The science of DNA analysis is an amazing tool that many genealogists
can benefit from in their efforts to link families together. However, like any
tool, it is important to understand what a DNA analysis can and cannot reveal.
Once you learn when to use DNA testing, you'll be able to solve genealogy problems
that otherwise might be unsolvable.
The most important aspect of DNA testing, or any research project for that matter,
is having an idea of what you want to determine, and defining the evidence that
will prove or disprove a conclusion. With DNA testing this means selecting the
right person (or people) to be tested. In some cases, testing the DNA of more
than one person is the only way to solve genealogy roadblocks. In order to know
whom to test, you must understand who has inherited the DNA in question.
Why Use Genetic Genealogy?
Ask yourself the following:
Are you looking to validate or invalidate genealogical records?
Do you think you may have a surname spelling change or adoption in your
line?
Are you looking to verify relationships with a family from a region where
you believe your line may have lived?
Do you believe, for any other reason, that you have a common ancestor
with another individual or group?
If you answered "yes" to any of these questions, then a Genetic Genealogy test
may help you find answers. Ancestry.com is once again offering several DNA testing
kits that are helpful in family history research. For more information, visit:
www.ancestry.com/rd/prodredir.asp?sourceid=831&key=P1025994
How it Helps
1. DNA Matching—Comparing your results (your ancestral signature) against
other people's DNA signatures can help you find new relatives and ancestors,
or ancestors for whom there are no written records. The two primary tests for
this purpose are the Y-chromosome test, and the Mitochondrial DNA sequencing. The Y-chromosome test relies on the male line while the Mitochondrial DNA sequencing needs a female line to test.
Both of these tests can be very helpful, but the Y-chromosome test has more
scientific studies to support its use for genealogical purposes. While the Mitochondrial
DNA sequencing is thought to be just as useful in proving relatedness, there
are fewer tools and studies available to help interpret the results.
2. Proving Relationships—Proving relationships is one of the most useful
aspects of DNA testing for genealogists. If you have a theory that two people
might be related in your pedigree, but you have been unable to locate any documentation
to prove your theory, DNA testing might be able to help. If the correct two
(or more) people have their DNA analyzed, a signature match will indicate that
they are closely related. A mismatch will confirm the two people are not closely
related.
Exact matches of Y-chromosome tests will indicate that the two people are related
within about five generations. If one or two markers on the signature are different,
the two people are still related but the relationship is likely too distant
to be genealogically relevant. A statistical model is used to determine the
most likely number of generations between the two people.
Exact matches of Mitochondrial DNA sequencing also indicate relatedness, but
there are not sufficient studies to determine the number of generations separating
the two people.
3. Surname/Clan Reconstruction & Regional Migration—This is another common
use of Y-chromosome tests (Y-chromosome Haplotype). Groups of families with
a common or similar surname origin might want to know if (and how) they are
related to one another. Individuals and groups can also discover genetic connection
to others living in a country where the family is thought to have lived within
a migration path. For example, a group of possibly related families with the
surname of "Thomas" wants to find out if they all have a common male ancestor
from whom they descended, who lived in a particular country. If a male surname
representative from each family submits his DNA for the Y-chromosome test, the
signatures can be compared to essentially reconstruct the tree back to a common
ancestor.
Some individuals or families may have completely different signatures indicating
they did not descend from the same common ancestor as the others. With a large
enough sample of signatures, it is possible to tell which branch of the Thomas
tree each family came from and how close that branch was to the common ancestor.
What DNA Testing Will Not Tell You
1. These tests will not reveal any information about your health or your predisposition
for certain diseases. These tests do not look at the regions of your DNA that
are associated with health information or genetic traits. Since the regions
being examined are between your genes, regions called "Junk DNA," nothing in
the results will imply any health-related information.
2. These tests do not create a unique personal genetic fingerprint that can
be used to identify you. Since you and other family members will have exact
matching results, these tests are not capable of proving unique identity. You
can think of these tests as a unique family fingerprint.
3. These tests do not tell you which ethnic tribe you may belong to or the exact
country of origin for your surname. They are designed, rather, to allow you
to discover these genealogical answers by comparing to others who are proven
to fall within certain genealogical characteristics.
Next month we will feature Part II in our series of Genetic Genealogy. For more
information about ordering DNA testing kits, go to:
www.ancestry.com/rd/prodredir.asp?sourceid=831&key=P1025994
Please direct any questions to Rachael McKinnon at: rmckinnon@myfamilyinc.com
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