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We are DNA testing at FamilyTree DNA a Houston, Texas based business. IF INTERESTED IN JOINING THIS GROUP AND YOU HAVE NOT DNA TESTED Please use the link provided in the links, to procure your testing kit. If you have tested with another company, please contact "Roberta Estes" ~~~~~~~~***~~~~~~~~ |
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Autosomal DNA Testing and Analysis
Unlike
yline and mtdna testing where the DNA of the father or mother is passed to the
offspring unmixed with that of the other parent, autosomal testing tests all
portions of the DNA of an individual. As
the field of genetic genealogy has moved forward, research has begun to indicate
that certain markers are found in higher or lower amounts in different ethnic
populations. For
example, if someone has the Duffy Null allele, or genetic marker, we know they
positively have African admixture. We
don’t know how much African admixture, or from which line, or when that
individual with African admixture entered their family tree, but we know for
sure they existed. Attempting
to determine the population frequency of varying markers and what that means
relative to other populations is the key to this analysis.
Few markers are simply present or absent in populations, but are found in
varying frequencies. Some
populations are widely studied in the research literature, and others are
virtually untouched. The process of
compiling this information in a meaningful manner so that it can be analyzed is
a formidable task, as the information is often found in nearly inaccessible
academic and forensic research publications.
It’s difficult to determine sometimes if the DNA analysis of 29
individuals in a small village in northern Italy is, for example, representative
of that village as a whole, of northern Italy, or more broadly for all of Italy
as a whole. Is it representative of
Italy today or Italy historically? These and other similar questions have to be answered fully
before the data from autosomal testing can be useful and reliable. If
the DNA tests being performed aren’t mtdna or yline, then they are autosomal
tests, meaning they are performed on the balance of the DNA contributed by both
parents to an individual. Before
we discuss the varying kinds of autosomal tests and what they mean, let’s take
a look at the inheritance process and how it really works. Inheritance Everyone
knows that you inherit half of your DNA from your mother and half from your
father. However, this isn’t
exactly true. While each child does
on the average receive half from each parent, the actual inheritance
pattern varies much more than that and each sibling may receive far more than
half of their markers from either parent. We
don’t understand today how inheritance traits are selected to be passed to
children. Some “groups” of
genetic material are inherited together, and you may wind up with more or less
genetic material from one of your parents.
In time, certain genetic “traits” will be lost in some descendants,
while not in others. Therefore, you
can’t figure actual inheritance percentages by using the 50% rule.
This means that if your father was 50% Native American, you are not
necessarily 25%, genetically speaking. You
may receive 40% Native genes and your sibling may receive 60%. Let’s
use the Duffy Null allele we mentioned earlier as an example.
This marker could have entered your DNA pedigree chart with a grandmother
who carried the allele but had no obvious visible African ancestral traits, or
from your father who might have been visibly African in ethnicity.
The Duffy Null allele, which is just one marker, could have been passed
in the inheritance of DNA for many generations, far after any visible African
traits had disappeared, or it could be one of many African traits passed from
parent to child. The
relevance of the Duffy Null allele is determined by the number of other
“African” markers that appear in high quantity.
If there are few other African markers, then your African ancestry was
likely further back in time. If
there are many, then your African ancestry was likely more recent.
These statistical calculations are how the importance of autosomal
markers are determined and how percentages or estimates of ethnicity are
calculated. Any
one allele or marker can be lost permanently in any generation.
Each child receives one gene from each parent. In the example below, let’s say that the mother carried
genetic markers A and B, and the father C and D, and D is the Duffy Null allele.
Mother
Father
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Markers
A B
C D Child
1 – A and C Child
2 – A and D Child
3 – B and C Child
4 – B and D You
can see that half the children received the D marker, but each inheritance event
was a random recombination of the markers.
It is also possible that none of the children would receive the D marker,
or all of them would receive it. Statistically
speaking, half will receive the marker, but statistics and individual
inheritance are two different things. Random
recombination is the reason why siblings who take autosomal tests sometimes show
significantly different results. You
can also see how a marker that is very old ancestrally, meaning introduced many
many generations ago, could be absent in one entire descendant line and present
in another line. From
the above examples, we see that we have two variables that we need to deal with
when attempting to use autosomal DNA for genealogy.
First,
we need to take into consideration inheritance patterns which we can’t
determine retrospectively without testing several descendant lines.
So, in essence, we can only deal with, and test, what we personally carry
today as our genetic inheritance. The
second variable is determining population frequency for a particular marker and
understanding its significance to us through comparative population genetics. This
is why autosomal testing can give us important hints, but are often considered
“unreliable”. The results
are highly subjective today, but increase in accuracy as more research is
completed, compiled, published and analyzed. Types
of Autosomal Tests There
are two types of autosomal tests used today for genetic genealogy. One type of test uses the Codis forensic markers and the
second type, biogeographical tests, use a much broader spectrum of marker
results. Let’s look at both
types of testing and the information they provide separately. Codis
markers are a standardized set of autosomal markers used for paternity testing.
Additionally, they are used by police departments and forensics labs.
The markers employed in these tests are selected specifically to differentiate
between people in order to identify them individually, not to find common
markers to place them in ethnic groups. The
results from these tests are only numbers, and the recipient is often left to
their own devices as to how to interpret the results.
These tests are available from numerous sources.
I prefer to interpret these results in conjunction with Yline and
mitochondrial DNA test results for as much of the genetic pedigree chart as can
be provided in order to obtain a more complete genetic picture. Below
is an example of what Codis test results look like.
They are very similar from any lab.
Location
Mother
Child
Analysis
of Codis Markers Unless
you’re using the Codis marker results to determine siblingship or some other
personal reason, these numbers are fairly useless genealogically. It’s the analysis of these markers that matters. There
are different avenues to analyze Codis results.
None are “right” or “wrong”.
At DNAexplain, we use a combination of resources, both public and
private, including Omnipop and other European and Canadian autosomal forensic
data bases. Tribes
(www.dnatribes.com) has been compiling
population data on these genetic markers for some years now and will compare
your autosomal results with their data base.
Take a look at their samples tab. Ironically,
the results may vary significantly between these resources.
There is no “right” or “wrong” answer at this point. I encourage
everyone to simply view these results as “data”, hints to puzzle pieces.
As the data bases improve and we better understand population migration
and movement, the clarity of the results will improve too. Tribes
early population tables did not include data from the British Isles, so their
results were highly skewed towards other world populations.
Omnipop today relies on self-reported ethnicity and does not include
normalized data (or a normalizing factor) for varying populations.
Because Tribes is a private company, we don’t know much about their
population data, whether it’s widely representative of the world population
distribution and whether it has been normalized or not.
Biogeographical
ancestry testing, available from DNA
Print Genomics (www.dnaprint.com), is the
second type of autosomal testing. They
test all of your genetic contributions for specific, proprietary markers that
indicate geographical heritage, not just the Yline or mtdna. They do not use the Codis markers, but use, depending on your
test selected, between 500 and 1349 markers they’ve discovered to be relevant
to ethnicity. This
test is currently available from only one source, although the test is resold by
several testing companies. Results
from this test are returned as percentages of ethnic heritage as shown below.
Your
results are reported within confidence bands, which indicate a range of
percentages that might actually be accurate.
This is shown above by the bands surrounding the red dot which shows the
“most likely” result. The
margin of error is often as high as 15%. Typically,
there is no dispute over the majority ancestral type.
However, minority types are apparently much more difficult to discern. Roberta
Estes, copyright 2006-2007, all rights reserved
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~~~~~~~~***~~~~~~~~ All Contents are Copyright © 2007 The Lost Colony Genealogy and DNA Research Group and the Lost Colony DNA Projects at FTDNA. The art work on this website is my (Nelda L. Percival) original art work and has not been released to any person or organization other then for the use of the Lost Colony Genealogy and DNA Research Group and the store front owned by the same. My art work has never been part of the Lost Colony Center for Science and Research's property. My art used here and at the store front was drawn precisely for the projects run by Roberta Estes and ownership has not been otherwise released. This project also uses the artwork of Dr. Ana Oquendo Pabon, the copyright to which she has retained as well. Other art works are the copyrights of the originators and may not be copied without their permission.All DNA Content on this site
belongs to the individuals who tested and or their representatives
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