Your DNA was derived from your mother and father, and theirs was derived from
their mothers and fathers, and so on. Five generations represents 32 direct ancestors
or approximately 125 years. Twenty generations includes 1,048,576 direct ancestors!
Through DNA analysis, you can discover your heritage.
DNA is passed down from generation to generation. It is made up of four nucleotides:
adenine, cytosine, thymine, and guanine. The order of these letters, A-C-T-G, makes
up the DNA sequence.
Chromosomes are the package for DNA and genes. We each have 23 pairs of chromosomes.
22 are autosomes. The 23rd pair is the sex chromosome. The 23rd chromosome from
the mother is always an X. A child inherits either an X or a Y chromosome. The chromosome
from the father determines the child’s gender. An X from the father would
result in an XX combination, which is female. A Y from the father would result in
an XY combination, resulting in a male child. So you want to find out about your
genealogy by DNA evaluation?
Scientists don't understand how inheritance traits are selected. Two offspring’s
from a set of parents may have different sets of chromosome pairs, and therefore
different ancestral proportions even though they were the product of the same male-female
union. This means if your mother was 50% Native American, you are not necessarily
25%. You may receive 10% Native genes and your sibling may receive 40%. For this
reason, DNA testing for heritage purposes may not give you the results you were
Your maternal copy of chromosome 1 could have been passed through your mother
from your maternal grandmother OR your maternal grandfather, but which one you received
was randomly determined at conception. The copy you receive from your mother is
actually a chimeric chromosome that includes parts from your grandfather and your
DNA Testing for Genealogy
Family Tree through DNA has added a new dimension to your ancestry. It
can help verify if you are putting the right people in your family tree. If you
have exhausted all sources and can’t go back any further, you can find out
at least what your ethnic and genetic make up is.
Y-Chromosome testing looks at segments of DNA found only in males. The Y-STR genealogy
DNA test is used to test males and their direct male relatives.The Y- Chromosome
is passed from father to son relatively unchanged through many generations. Because
the Y- Chromosome follows the same father-to-son pattern much like surnames in Western
culture, the test has also been referred to as a "Surname Test."
MtDNA testing looks at the DNA inherited from your maternal ancestors. The two
most common mtDNA tests are a sequence of HVR1 (Hypervariable Region 1) and a sequence
of both HVR1 and HVR2.
Single nucleotide polymorphism (SNP) markers have an extremely low mutation rate.
SNP markers, can indicate your haplogroup. There are at least two million SNPs in
the human genome. Y-STR tests can predict your personal haplotype. Haplogroups are
large groups of haplotypes. These results establish your deep ancestral origins
dating back thousands of years, often geographically oriented. The haplogroups for
males and females is different. Genealogy DNA tests show there is a rough overlap
between Y-DNA and mtDNA haplogroups. If a female is tested and belongs to haplogroups
A, B, C, D or X, and a male tested belongs to haplogroups Q or C3, they both would
belong in whole or part, to a Native American group.
Autosomal STR markers, looks at the genetic material inherited from the mother
and father in a lineal and non-lineal fashion. Each person inherits a unique combination
of the autosomal STRs. It will help to identify the individual ethnic group and
world regions where a person’s total combination of ancestry is most frequent
or common. Some feel there are large margins of error with DNA analysis.
Family Heritage is Revealed through Markers
Most tests use STR markers known as short tandem repeats. The number of “repeats”
of the same DNA sequence of A-C-T-G is known as “Alleles”. The markers
are designated by a number. Example: one marker being tested could be DYS393 (DNA
Y-Chromosome Segment) and results for the repetition of the sequence [AGAT] is 12.
Thus the marker DYS393 has an allele of 12.
There are over 100 markers, but most tests available are for 12 to 67 markers.
The more markers you have tested, the greater the cost, but also narrows down your
results with greater accuracy. If you test 12 markers, and you have another relative
with the same surname, and
same results (for the same STR markers and allele’s), your MCRA (most common
recent ancestor) is between 7 and 29 generations ago. If you test 37 markers, your
MCRA is between 2 and 7 generations ago. If you test 67 markers, your MCRA is between
2 and 6 generations ago. If you have a perfect match 12/12 with someone who does
not have the same last name, your MCRA is probably about 1,000 years ago or 40 generations.
If your last name is the same or a variant, then a match of 37/37 markers, gives
you a 50% chance of having a MCRA within 5 generations.
The companies that are doing testing do not use the same database or testing procedures.
Therefore the same test, done at different companies, may result in different outcomes.
This was uncovered when Oprah Winfrey and 60 Minutes did a segment revealing the
same tests done from three (3) different companies, all had different results.
Comparing Testing Results
Y-Search is one company, pulling results from various genealogy DNA testing companies
in an effort to help you find other people that have taken DNA tests from different
companies to provide a link for possible genealogy matches. But remember, if your
last name is not the same, your MCRA is about 1,000 years ago and will most likely
not help you in your family research.
Genealogy and DNA testing gives an ancient picture of your family and traces your
roots back several thousands of years. A Y-STR comparison DNA analysis can achieve
a probability of a relationship between a child, and his mother and father using
a paternity Index (PI). The PI’s for each marker are multiplied with each
other to produce a combined paternity index (CPI), which represents the overall
odds, that an untested male would have the same results if his genetic profile were
compared with the child’s. The CPI is then converted into a Probability of
Paternity value, which specifies the probability that the tested man is the father.
Discover your Family Roots through Migration Paths
Another way to find your
ancestors, is to do research on colonial migration routes and roads. Understanding
why your ancestors moved, and where they settled can give you a bit of history that
DNA tests can't and you might understand a little bit more about your own family roots.