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URL:  http://boards.fool.com/if-the-dna-is-not-essentially-identical-then-how-30407584.aspx

Subject:  Re: Skin cells reveal DNA’s genetic mosaic Date:  11/30/2012  5:00 PM
Author:  adonsant Number:  23973 of 24925

If the DNA is not essentially identical, then how can a PCR (or whatever the latest version of this test is called) determine parentage? If the DNA is a little different from cell to cell, I would think you could get different results every time you ran the test.

When you try to determine parentage by DNA testing (probably by microsatellite analysis, IIRC), you're not just examining one cell. You're examining a population somewhere on the order of 10,000 to 100,000 cells. So, even though every cell is a little different from every other cell, >99.9% of the cells are identical at any given position in the genome. Thus, you don't see the small differences between cells. You get the most common version, which almost always is going to be what the fertilized egg had.

Speaking of genetic change, there was a talk I heard last year about transposon mobilization in neurons and how that might be involved in generating more diversity in the brain. This review might be of interest:

http://www.ncbi.nlm.nih.gov/pubmed/22201983

I don't know if it's freely available.

-Anthony
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