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Old 10-20-2017, 02:51 PM
 
Location: Brusssels
1,934 posts, read 3,492,558 times
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Quote:
Originally Posted by cjseliga View Post
Interesting article in the Philly papers today, which many, I assume, already knew about DNA results:

These siblings took DNA tests and got different results. Why determining ancestry is rarely accurate

Our Italy/Greek numbers were about the same. But her results showed 37 percent British Isles, whereas I was 53 percent. She also showed 10 percent Scandinavian and 7 percent East Europe — neither of which even appeared in my results. And we’re about as Scandinavian-looking as Jennifer Lopez.

“It’s very difficult to accurately find your ancestry under any circumstances,” said Jonathan Marks, an anthropology professor at the University of North Carolina at Charlotte. “There has been genetic mixing for thousands of years. These tests are fun but rarely accurate — 10 percent Scandinavian could be no Scandinavian because the test could very easily be 10 or 15 percent off.”

“The methodology they use in determining the DNA markers is solid,” said Deborah Bolnick, an anthropology professor at the University of Texas. “The challenges come with interpreting those DNA sequences to say something accurate about your ancestry.”
This is also pretty common since not every child gets an equal share of each part of their parents' DNA.
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Old 10-20-2017, 04:54 PM
 
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Recombination.

Mendelianism.
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Old 10-20-2017, 10:16 PM
 
Location: Chapel Hill, NC, formerly DC and Phila
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I read a comment on another genealogy board today that described the phenomenon well. Think of your parents' DNA as a pot of stew. The stew is made up of carrots, potatoes, onions, etc. You and your siblings are all given a ladle-full of stew. Your ladle's worth might have lots of carrots, some onions, and few potatoes. Your sister's ladle might have lots of potatoes, some onions and few carrots. Your brother's ladle might have lots of carrots, few onions, and some potatoes.
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Old 10-21-2017, 01:44 PM
 
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Quote:
Originally Posted by ozarknation View Post
We are NOT identical. Not even twins are identical. The only persons identical to each other are CLONES.
I thought identical twins could be considered clones unless after they fissured, one developed a genetic mutation.

Anyways with ancient DNA it gets even more fuzzy, since you have a greater potential for contamination & deterioration.
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Old 10-21-2017, 06:52 PM
 
Location: Colorado (PA at heart)
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Quote:
Originally Posted by kovert View Post
I thought identical twins could be considered clones unless after they fissured, one developed a genetic mutation.
Yes, identical twins are genetically identical. I'm not sure what the other response is talking about.

https://isogg.org/wiki/Autosomal_DNA_statistics#Table
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Old 10-25-2017, 05:51 PM
 
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Quote:
Originally Posted by PA2UK View Post
Yes, identical twins are genetically identical. I'm not sure what the other response is talking about.

https://isogg.org/wiki/Autosomal_DNA_statistics#Table
Thanks for the clarification.
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Old 10-25-2017, 07:53 PM
 
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Somewhat difficult to grasp at times, but it is theoretically possible for a brother-sister pair with the same parents to share zero chromosomal DNA. Unlike but a statistical possibility. It's all about how those 48 chromosomes segregate when they go to zygotes.
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Old 10-26-2017, 02:01 AM
 
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Quote:
Originally Posted by PA2UK View Post
Yes, identical twins are genetically identical. I'm not sure what the other response is talking about.

https://isogg.org/wiki/Autosomal_DNA_statistics#Table
Maybe they were thinking of fraternal twins? They just mentioned twins, not identical.
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Old 10-26-2017, 08:31 PM
 
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RE identical twins being identical at the DNA level: chromosomal DNA undergoes gene rearrangement throughout one's lifetime. So while identical twins start out identical, they actually "diverge" over time. These changes would be below the level of detection of typicial genealogy analyses though.
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Old 10-26-2017, 09:27 PM
 
Location: Georgia, USA
25,137 posts, read 30,041,038 times
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Quote:
Originally Posted by Prumio View Post
RE identical twins being identical at the DNA level: chromosomal DNA undergoes gene rearrangement throughout one's lifetime. So while identical twins start out identical, they actually "diverge" over time. These changes would be below the level of detection of typicial genealogy analyses though.
https://www.scientificamerican.com/a...not-identical/

https://wstwinregistry.org/2015/10/0...male-mz-twins/

Why identicals might have different ancestry results at a genealogy testing service:

Understanding Genetics

Last edited by suzy_q2010; 10-26-2017 at 10:03 PM..
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