DNA Genealogy
The next time you are watching your favorite CSI TV show or a
particular movie and stumble into the fascinating world of DNA,
you might be surprised to know that our DNA can do more than
identify a suspect or victim at a crime scene. In fact, DNA is
now being used to identify ancestors in the new and exciting
field of DNA Genealogy.
DNA Genealogy takes traditional
genealogy and applies genetics to it. DNA Genealogy involves the
use of genealogical DNA testing to determine the level of
genetic relationship between two individuals (Genealogical
2005). DNA, deoxyribonucleic acid, is used in the process
because of its unique nature and the fact that it is passed down
from one generation to the next. In the passing, some parts of
the DNA remain almost completely unchanged, while other parts
change dramatically. This property allows for the identification
of certain consistencies between generations and provides the
ability to identify genetic relationships.
There are two types of DNA tests available for testing DNA Genealogy: Mitochondrial DNA
(mtDNA) and Y-chromosome DNA tests.
Mitochondrial DNA (mtDNA) is found in the cytoplasm of the cell
instead of in the nucleus as is Y-chromosome (Tracing 2003).
mtDNA is passed by a mother to both her male and female children
without any additions or mixing from the father. Therefore, your
mtDNA is the same as your mother's mtDNA. mtDNA is different in
nature compared to Y-DNA. It changes slowly making it more
difficult to determine close relationships and easier to
determine relatedness. If two people have the same mtDNA, there
is a very good chance that they also share a common maternal
ancestor. Unfortunately, it is difficult to determine if that
common maternal ancestor was recent or instead lived hundreds of
years ago.
Y-chromosome tests have been used more and more recently to
determine DNA Genealogy. The Y-DNA tests are
only available for males, because the Y-chromosome is only
passed down along the paternal line from father to son. There
are tiny chemical markers on the Y-chromosome that create a
unique pattern. This pattern of markers is what is called a
haplotype. A haplotype is used to determine one male lineage
from another. This type of testing is often used to determine if
two individuals who have the same surname share a common
ancestor.
One of the early beginnings of DNA Genealogy was a study
published by Bryan Sykes in 2000 (Sykes and Irven 2000) that
used DNA Genealogy (Y-chromosome markers) along with surname
studies to determine relatedness. The study compared 48 men with
the same surname of Sykes from the regions of England and
analyzed four Short Tandem Repeats (STRs) on their Y-chromosome:
DYS19, DYS390, DYS391, and DYS393. The study found that of the
48 men tested, 21 had the same core haplotype and many others
were only one mutational step away from the core haplotype.
Skypes interpreted these results to reveal a common origin from
an ancestor who lived some 700 years ago (Butler 2005).
Since its early beginnings, DNA Genealogy has come a long way and
has grown rapidly. DNA Genealogy continues to increase in
popularity as the price of tests becomes much more affordable
and the number of markers and clarity of the tests become
greater. Additionally, DNA collection techniques make it a very
simple and pain-free process.
Sources
Butler J. (2005) Forensic DNA Typing; Biology, Technology, and
Genetics of STR Markers, 74, 231-232.
Genealogical DNA test. (2005, December 7). Wikipedia, The Free
Encyclopedia. Retrieved 21:52, December 8, 2005 from
http://en.wikipedia.org/w/index.php?title=Genealogical_DNA_test&o
ldid=30489865.
Sykes, B. and Irven, C. (2000) American Journal of Human
Genetics, 66, 1417-1419.
Tracing Your Ancestry Through DNA (2003) Genealogy.com.
http://genealogy.about.com/cs/geneticgenealogy/a/dna_tests.htm