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Author: bdhinton Big gold star, 5000 posts 10+ Year Anniversary! Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: of 25067  
Subject: Skin cells reveal DNA’s genetic mosaic Date: 11/29/2012 9:29 AM
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The prevailing wisdom has been that every cell in the body contains identical DNA. However, a new study of stem cells derived from the skin has found that genetic variations are widespread in the body's tissues, a finding with profound implications for genetic screening, according to Yale School of Medicine researchers.

http://news.yale.edu/2012/11/18/skin-cells-reveal-dna-s-gene...
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Author: NigelGlitter Big red star, 1000 posts Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 23948 of 25067
Subject: Re: Skin cells reveal DNA’s genetic mosaic Date: 11/29/2012 1:35 PM
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Different DNA. More living cells from other life forms than our own inside us. A tarp, over a glove, over a shell build out that still uses ancient parts integrated into the newer to function.

Regardless of how you think we got here, the human body is pretty damned amazing.

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Author: 1poorguy Big funky green star, 20000 posts Top Recommended Fools Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 23956 of 25067
Subject: Re: Skin cells reveal DNA’s genetic mosaic Date: 11/29/2012 4:28 PM
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quibble: not just the human body. Pretty much all mammalians are freakin' amazing. Or, heck, extend it to all vertebrates. How the DNA works, and all the biochemistry that makes the 'machine' work...remarkable.

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Author: adonsant Big red star, 1000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 23963 of 25067
Subject: Re: Skin cells reveal DNA’s genetic mosaic Date: 11/29/2012 5:53 PM
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It sounds like a cool study. I would take exception with the first paragraph (guessing it was written by a non-biologist). I don't think anyone believed that every cell in the body contains identical DNA. If this were true, we wouldn't get cancer, for starters. Work on mammalian enzymes invovled in DNA synthesis have suggested that point mutation rates (changes in a single 'letter') are roughly one per cell division. However, to the best of my knowledge, no one has really looked at mutation rates in a real living organism or documented how significant it is.

Based on the news blurb,* what's interesting about this study is that it's the first to really start quantifying the error rates in vivo. It would be interesting to look at other tissues to see if the skin is more likely to develop mutations, presumably due to UV and/or chemical exposure, and to see how it changes as we grow older. It also may have important consequences for the use of iPS cells in therapies, depending on what the data specifically show.

-Anthony

*There was no November 18th issue of Nature this year, and I'm not finding it within the last few weeks or with their search engine. Thus, I haven't actually read the study. Hopefully it comes out soon.

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Author: 1poorguy Big funky green star, 20000 posts Top Recommended Fools Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 23964 of 25067
Subject: Re: Skin cells reveal DNA’s genetic mosaic Date: 11/29/2012 6:00 PM
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Anthony,

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.

1poorguy

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Author: 0x6a74 Big funky green star, 20000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 23965 of 25067
Subject: Re: Skin cells reveal DNA’s genetic mosaic Date: 11/29/2012 6:13 PM
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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.



i was wondering the same thing ..only for crime-lab stuff


=

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Author: NigelGlitter Big red star, 1000 posts Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 23967 of 25067
Subject: Re: Skin cells reveal DNA’s genetic mosaic Date: 11/29/2012 7:59 PM
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i was wondering the same thing ..only for crime-lab stuff

Yeah. Me too. If the cells are different, how different? Is a DNA match still more reliable than eyewitness recollection?

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Author: 0x6a74 Big funky green star, 20000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 23968 of 25067
Subject: Re: Skin cells reveal DNA’s genetic mosaic Date: 11/29/2012 9:43 PM
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Yeah. Me too. If the cells are different, how different? Is a DNA match still more reliable than eyewitness recollection?


" eyewitness recollection" a rather low bar ...
unless you're thinking of Biblical witnesses

(>:

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Author: adonsant Big red star, 1000 posts Old School Fool Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 23973 of 25067
Subject: Re: Skin cells reveal DNA’s genetic mosaic Date: 11/30/2012 5:00 PM
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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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Author: feedmeNOWhuman Big funky green star, 20000 posts Top Recommended Fools Old School Fool CAPS All Star Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: 23985 of 25067
Subject: Re: Skin cells reveal DNA’s genetic mosaic Date: 12/2/2012 8:10 PM
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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.



I don't have the book in front of me, but I read recently that every time a cell reproduces, a small amount of information is lost. Something on the order of a few hundred base pairs, IIRC. There's a possibility this is related to what causes aging.

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