African American DNA Research Forum
Re: Question about DNA Admixture Tests
In Response To: Re: Question about DNA Admixture Tests ()
As I mentioned in an earlier post (18 April 2006) about this testing, this is very confusing stuff. I've had to read and re-read so much of it that it's not even funny. At any rate, here's (what I think is) the explanation to your question:
Your DNA was derived from your mother and father, and theirs was derived from their mothers and fathers, and theirs from their parents and so on. You have 23 pairs of chromosomes. 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 (you could not have received both). Most of the time this chromosome 1 copy that you receive from your mother is actually a chimeric chromosome that includes parts from your grandfather and your grandmother. Recombination is the process by which these chimeric chromosomes are created and occurs at least once on each chromosome every time a new sperm or egg cell is made. As such, although blending does not occur at the level of the gene (the unit of trait expression) our chromosomes are mixed together and so our genomes contain segments of DNA from all of our ancestors. In contrast, the mitochondrial DNA or Y-chromosome test can only provide data on one single lineage of ancestors each generation into the past. For example, 10 generations ago (year 1802 at 20 years per generation), a baby born today has 1024 ancestors. By measuring your ancestral proportions using a genomics method, we are actually measuring the average population affiliations of all of these 1024 ancestors. Since random processes (recombination and independent assortment) at inception determines the mixings and pairings you harbor, two offspring 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. For example, an employee of our company is a European male who married a Hispanic woman and had three children of mixed descent. Each of the children exhibits their own unique proportionality, which you can see by clicking on casestudy. If these two had an infinite number of children, the average would correspond to that proportionality exactly between the mother and father, but each child would deviate from this average by a unique and random amount.
You can read more at the website listed below.
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