Afrocentrism and other ideas making inroad in Afro-Latinos

Salsassin · **Joined:** Mon 04 Apr 2005 15:59 **Posts:** 3515

On Autosomal versus Y Chromosome and mtDNA

Quote:

From: Lou Charlton [mailto:LCharlton@dnaprint.com]
You absolutely cannot compare the Y-chromosome and Mitochondrial DNA tests with DNAPrint's autosomal tests. It would be like trying to compare the proverbial "apples and oranges". The Y and Mito tests only look at genetic inheritance from the point of view of the sex chromosomes. There are only 2 pairs of sex chromostomes they deal with: XX or XY. When meiosis occurs they split into two single chromosomes, either Xs or Ys. If 2 Xs come together at mating, a girl ensues; if an X and Y chromosome come together the resultant offspring is a boy. The X and Y tests are haploid - meaning showing only 1/2 of the total possibility between the two sex chromosomes.

We are endowed with 23 pairs of chromosomes (46 total chromosomes) of which only one pair comprise the sex chromosomes. DNAPrint's autosomal tests look at all the other chromosomes, the autosomes. The test specifically excludes the sex chromosomes so you can NOT compare the results of the two types of tests. Additionally, the AncestrybyDNA 2.5 test and the Euro-DNA 1.0 test look at DNA that has resulted from the past historical matings of all the males PLUS females in your history, not just the male line only (Y) or the female line only (Mito).

In this ancestral picture, the thousands of markers that have come together between the males and females do come together totally randomly. That is why you can not predict certain percentages from any particular ancestor or ancestral line. If you look at the total numbers of ancestors you are dealing with in this test, if we only go back 15 generations (around only 500 years ago), a person has 32,000 ancestors; 20 generations ago they had more than a million ancestors. When you think of how many markers this involves all randomly combining at each historical mating PLUS the many mutations that might have occurred along the way, you can see the possible results as being a random recombination of the DNA each and every time.

The DNAPrint AncestrybyDNA 2.5 test tells your biogeographical ancestral percentages as defined by anthropologists: Indo-European, Native American, East Asian and sub-Saharan African. A person's DNA is a composite of these percentages that add up to 100%. Because of the randomness of the recombinant DNA from each male and female ancestor that mated in one's past, you can not predict percentages in any single person's DNA. We are all different and as unique as snowflakes.
Emanuela I. Charlton, Ph.D.
Customer Service

fwsweet · **Posted:** Thu 01 Jun 2006 17:00

Salsassin wrote:

On Autosomal versus Y Chromosome and mtDNA

The above difference cannot be explained often enough. Autosomal mapping tells your genetic makeup but cannot tell anything about specific ancestors and their tales. Matrilineal and patrilineal lineages tell nothing about your genetic makeup but tell stories of the populations to which those specific ancestors belonged. Ultimately, genealogy is a search for interesting tales among your millions of ancestors, so the latter (matrlineal/patrilineal) technique is often more useful to a genealogist. The former (autosomal mapping) may complement it because it may show ancestry that you had not expected, but it is more useful to historians and anthropologists than to genealogists.

I have two sessions at the Melungeon Sixth Union, next week. They are both listed at http://www.melungeon.org/index.cgi?BISKIT=1140325212&CONTEXT=cat&cat=10117. The first session (Friday) is The Triumph of the One-Drop Rule. According to the schedule, the second session (Saturday) is titled, "Informal Follow-Up: History and Molecular Anthropology of the Color Line." I am not quite sure yet, what the second session will cover. I had hoped to discuss this very topic (matrilineal/patrilineal versus autosomal mapping) with the genealogists there.

Salsassin · **Joined:** Mon 04 Apr 2005 15:59 **Posts:** 3515

How could autosomal and mt-dna be SO different though? I mean one claiming more than 40% matrilineal Taino contribution and the other claiming 8% overall contribution? Something still sounds off.

oevega · **Posted:** Thu 01 Jun 2006 18:49

Salsassin wrote:

How could autosomal and mt-dna be SO different though? I mean one claiming more than 40% matrilineal Taino contribution and the other claiming 8% overall contribution? Something still sounds off.

The same happens in Argentina. There people looks white, but have even more Amerindian mtDNA (50%).

Omar

William · **Posted:** Thu 01 Jun 2006 18:52

Salsassin wrote:

How could autosomal and mt-dna be SO different though? I mean one claiming more than 40% matrilineal Taino contribution and the other claiming 8% overall contribution? Something still sounds off.

mtDNA and Y results are most useful for determing that admixture occurred, and for determing if there was a sexual bias, i.e., foreign males mixing with indigenous females, or vice-versa. I personally am skeptical of using mtDNA and Y for estimating overall admixture. If a study finds 5 sub-Saharan mtDNA markers out of 100 people studied in a given population, and the authors make the claim that admixture in that population runs at a rate of 5%, what they really are saying is that in that particular sample, sub-Saharan mtDNA (not overall DNA) runs at that rate. Autosomal testing is far more accurate when it comes to determing true admixture proportions. It is not surprising that autosomal and mtDNA or Y test results are often at variance with one another. Also, as I mention in the "Jodie" thread, all test results (even of the same kind) will differ simply because of different samples.

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