Genetic Testing Has Great Impact on Genealogy
(Reprinted with Permission from the Tribune-Star)
Written by Tamie Dehler
While the 20th century changed genealogy
forever by introducing the use of the computer, the 21st century is
changing how we do family research by bringing genetic testing solidly
into the field of genealogy. More and more people are opting for genetic
testing of their family lines to reveal whether the people in the lines
are truly related. One of the tests currently on the market is the
mitochondrial DNA test, mtDNA for short. The mtDNA test is unique in that
it determines a relation ship to a female line, through only the females
in that line.
Here’s how it works:
We all learned in elementary school that
mitochondria are small, rice-shaped structures located in each of the
body’s cells. We call mitochondria “the powerhouse of the cell”
because sugar is broken down into energy in the mitochondria. Because of
this function, the mitochondria have their own DNA, consisting of just 37
genes (very tiny DNA strands) to create the 13 proteins needed to do their
work of changing sugar to energy. But unlike the DNA in the nucleus of
human cells (which come from a person’s father and mother combined), all
mtDNA comes only from your mother and has been passed down from other to
mother since the beginning of humanity. MtDNA has a very slow rate of
mutation. Because mtDNA barely changes over time, it can be used to show
general distant relationships to a female ancestor. It establishes
mother-to-mother links all the way back in a female line.
When you take an mtDNA test, which is a simple
procedure you can do in your own home, the test will examine two regions
on the mtDNA called HRVC1 and HRV2, which are inherited from your mother’s
maternal line and will give you your “maternal signature.” If your
“maternal signature” is an exact match with others in your line, then
there is an excellent chance you all share the same common maternal
ancestor. Since the mtDNA is passed from a mother to all of her children,
both men and women can take the mtDNA test to see if they are related to a
common female ancestor through their mother, their mother’s mother, etc.
However, only the daughters in a line will continue to pass on the mtDNA
of that female line to their children. The sons, when they marry and have
children, do not pass on any mtDNA. The man’s children would all
have the mtDNA of his wife’s maternal line, passed on to his children
from their mother.
MtDNA testing also can determine what part of
the world your female line originated from since haplogroups (people
living in certain geographic areas) share common mtDNA patterns. This can
help the researchers find the ethnic or geographical origins of his/her
ancestors. MtDNA testing can also determine American Indian descent from a
female line. As you can see, this test is very useful and probably will
grow in popularity as more and more people utilize it.
Ancestry.com
is already in the process of building a mitochondrial DNA database for use
by its customers. In the future, family researchers will be able to take
the mtDNA test and then go to one of these databases to compare their
results with others from the same maternal line, thus establishing that
true relationships exist between different lines.
There is currently an mtDNA concordance. For more on this subject you can
find links at the
Ancestry.Com
website. This is a repository of all publicly available mtDNA studies and
the mutations observed.
(Tammy Dehler writes genealogy articles in the Sunday Tribune-Star
published in Terre Haute, IN.)