Archiver > GENEALOGY-DNA > 2004-02 > 1077466147

Subject: Re: [DNA] Ancient and Recent [was: How many actual markers...]
Date: Sun, 22 Feb 2004 11:09:07 EST

In a message dated 02/22/04 6:35:17 AM Pacific Standard Time,

> With all that has been said here, am I, the newbie, right in assuming that
> this testing really only pertains to the ancient genes of the testee versus
> the more recent gene acquisitions?
> I became interested in this process after discovering that my parental
> lineage demanded identity from two resources (historical) that insisted
> either one of two groups: African vs Amerindian in the last 5 generations,
> mine included.
> Also, does this mean that I would need to find a female descendant to trace
> this ancestry from a female lineage to get a more accurate result?

Reading between the lines, I gather you ordered the DNAPrint test (also known
as Ancestry by DNA or BioGeographical Ancestry). If we are counting
generations the same way, then

1) Your great-great grandparent (100% African OR Native American -- I'll just
say African from now on) marries a 100% European

2) Your great-grandparent (exactly 50% African) marries a 100% European

3) Your grandparent (approximately 25% African) marries a 100% European

4) Your parent (approximately 12.5% African) marries a 100% European

5) You are approximately 6.25% African.

There is randomness in the way genetic markers are passed on. When your
parent created the sperm or egg for you, he/she was passing on a genetic marker
that came from one of your grandparents, but you don't know which one. On the
average, you will get about 25% of your markers from each of your grandparents,
but it's just like dealing a hand from a deck of cards. You don't always end up
with equal numbers of hearts, diamonds, spades, and clubs. It's conceivable
that you would not have ended up with any African "diamonds," even if you would
expect 6.25% of your markers to be "diamonds" on the average.

Also, if your great-great grandparent was not 100% to begin with, your
pecentages would drop. One the other hand, if some of the spouses were not 100%
European, your percentages could increase, but they wouldn't be relevant to your
fundamental question. There is also uncertainty in what the markers reveal
about ancestry from a specific group. For example, one version of the marker (an
"allele") might be found in 83% of the African population and 9% of the
European population. If you have that marker, the odds favor an African ancestor, but
it could have been a European ancestor. The uncertainty is probably similar
to your expected percentage of African ancestry.

All the above is a very long-winded way of saying that you may or may not
learn the answer to your mystery with the DNAPrint test. We will be very
interested to hear about your results when they come in.

If #1 above was a female African, AND her maternal line was African all the
way back, then her straight female line descendants would carry mitochondrial
DNA that is typical of Africans. If #1 above was a male African, then the
straight male line descendants would have Y chromosomes typical of Africans. Using
Y or mtDNA gives you a clearer picture, because it doesn't get randomly
shuffled with the mtDNA of spouses. The downside is that it only reveals one of your
many ancestral lines, and it may be difficult to find the right person to
test. But if you succeed, then you should be able to settle the debate.

Ann Turner - GENEALOGY-DNA List Administrator
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