Genetic Ancestry
Testing: Is it Ready for Prime Time?
There has always been the need for humans to connect with
one another. Way before the term “social
networking” was invented genealogists were trying to increase their knowledge
of their family history through historical society files and newsletters
circulated via postal mail. With the
advent of the Internet online mailing lists, message boards and family tree
databases have become popular. Many
individuals are now prepared to go a step further in their search for their
ethnic mix, distant relatives and new ancestors through the use of direct to
consumer genetic ancestry testing. As
with all self-initiated genetic testing, buyer beware. Be
sure to research thoroughly before participating and if you have any questions,
contact your healthcare provider or a genetic counselor. You can find a counselor in your area at www.nsgc.org
According to the Genetics Home Reference (https://ghr.nlm.nih.gov) “genetic ancestry
testing or genetic genealogy is a way for people interested in family history
(genealogy) to go beyond what they can learn from relatives or historical
documentation. Examination of DNA
variations can provide clues about where a person’s ancestors might come from
and about relationships between families. Certain patterns of genetic
variations are often shared among people of particular backgrounds. The more
closely related two individuals, families or populations are the more patterns
of variation they typically share.”[1]
Three types of genetic
ancestry testing are commonly used for genealogy:
- Y chromosome testing: Variations in the Y
chromosome, passed exclusively from father to son, can be used to explore ancestry
in the direct male line. Y chromosome testing can only be done on males,
because females do not have a Y chromosome. Because the Y chromosome is passed on in the
same pattern as are family names in many cultures, Y chromosome testing is
often used to investigate questions such as whether two families with the same
surname are related.
- Mitochondrial DNA testing: This type of testing
identifies genetic variations in mitochondrial DNA. Although most DNA is
packaged in chromosomes within the cell nucleus, cell structures called mitochondria
also have a small amount of their own DNA (known as mitochondrial DNA). Both
males and females have mitochondrial DNA, which is passed on from their
mothers, so this type of testing can be used by either sex. It provides
information about the direct female ancestral line. Mitochondrial DNA testing
can be useful for genealogy because it preserves information about female
ancestors that may be lost from the historical record because of the way
surnames are often passed down.
- Single nucleotide polymorphism
(https://ghr.nlm.nih.gov/primer/genomicresearch/snp) testing: These tests
evaluate large numbers of variations (single nucleotide polymorphisms or SNPs)
across a person’s entire genome. The results are compared with those of others who
have taken the tests to provide an estimate of a person's ethnic background.
For example, the pattern of SNPs might indicate that a person's ancestry is
approximately 50 percent African, 25 percent European, 20 percent Asian, and 5
percent unknown. Genealogists use this type of test because Y chromosome and
mitochondrial DNA test results, which represent only single ancestral lines, do
not capture the overall ethnic background of an individual.[2]
Genetic ancestry testing has a number of limitations. Test providers compare individuals’ test
results to different databases of
previous tests, so ethnicity estimates may not be consistent from one provider
to another. Also, because most human
populations have migrated many times throughout their history and mixed with
nearby groups, ethnicity estimates based on genetic testing may differ from an
individual’s expectations. In ethnic groups with a smaller range of variation
due to the group’s size and history, most members may share many SNPs and it
may be difficult to distinguish people who have a relatively recent common
ancestor. The impact of ancestry testing on people, families, communities and
societies could bring to the fore a wide range of psychosocial, ethical, legal,
political and health related issues that need to be addressed. For more information, visit The Legal
Genealogist at www.legalgenealogist.com
An autosomal DNA testing comparison
chart is available at www.isogg.org/wiki/Autosomal__DNA_testing_comparison_chart
Genetic ancestry testing is offered by several companies and
organizations. Most companies provide
online forums and other services to allow individuals who have been tested to
share and discuss their results with others, which may allow them to discover
previously unknown relationships. On a
larger scale, combined genetic ancestry test results from many people can be
used by scientists to explore the history of populations, their migrations
patterns and how they intermingled with other groups.[3]
Additional information about genetic ancestry testing:
The University of Utah provides video tutorials (http://learn.genetics.utah.edu/content/basics/molgen/) on molecular genealogy.
The International Society of Genetic Genealogy
(http://www.isogg.org/) promotes the use of DNA testing in genealogy.
The American Society of Human Genetics (ASHG) developed a position paper on ancestry testing
(http://www.ashg.org/pdf/ASHGAncestryTestingStatement_FINAL.pdf).
Detailed information about genetic ancestry testing
(http://archive.senseaboutscience.org/pages/genetic-ancestry-testing.html)
is available from Sense About Science.
The Smithsonian National Museum of Natural History's
exhibit 'Genome: Unlocking Life's Code' discusses genetic ancestry testing
(http://unlockinglifescode.org/explore/our-genomic-journey/our-origins-and-ancestry).
The exhibit also discusses the African Diaspora
(http://unlockinglifescode.org/explore/our-genomic-journey/feature-story-african-diaspora)
and its influence on heredity and genealogy.
[1] Genetics
Home Reference – https://ghr.nlm.nih./GeneticTesting
, pg. 25
[2] Ibid.,
pg.25
[3] Ibid.,
pg. 26
