Saturday, June 23, 2012

“I don’t know nothin’ ‘bout understandin’ no DNA" - Autosomal DNA

When it comes to DNA, many of you, like me, might be scratching your head and saying (to paraphrase Prissie in Gone with the Wind), “I don’t know nothin’ ‘bout understandin’ no DNA.”  Boy, do I wish I would have taken time out from doodling and playing cootie catcher to listen to at least a couple of my science teachers. 

The University of Utah has put together four short little videos explaining the four kinds of DNA – Autosomal DNA, X Chromosome DNA, Y Chromosome DNA, and Mitochondrial DNA.  Currently, three of these types of DNA - Autosomal, YDNA and mtDNA (mitochondrial) are being used for genealogical purposes. 

The type of DNA that Ancestry used to predict my genetic ethnicity is autosomal.  If you are interested in understanding autosomal (a whole lot had better than yours truly could hope to explain) take a peak now at U of U’s autosomal DNA video.  

In a nutshell, each of us has 23 pairs of chromosomes.  Autosomal DNA looks at 22 of these pairs (the 23rd pair is the XY or XX chromosomes that determine a person’s sex.) 

You have inherited ½ your father’s autosomal chromosomes and ½ of your mother’s autosomal chromosomes.  But that also means that you lost half of each of your parents’ autosomal chromosomes. Likewise, your parents only inherited ½ of their parents’ autosomal chromosome etc.   

This is why your siblings’ genetic ethnicity might not look precisely the same as yours – they might have inherited different chunks of your parents’ DNA.  It’s also, why you and a cousin can take the test and not come up a match, yet you and a fourth cousin are.  It’s all in how the chromosomes recombined.

If you read the paper, “Melungeons, A Multi-Ethnic Population by Roberta J Estes, Jack H. Goins, Penny Ferguson and Janet Lewis Crain, you will see that the prediction of how much of the DNA I probably carry from my 4th great grandparents, Nimrod and Frances Thacker, is less than 1%.  If you factor in the probability that the individual who supplied the mixed race part of their DNA could have been 50, 100 or 200 years prior to their births – well, you can see why my autosomal DNA might not have picked it up.

For some of you who are descendants of the Vinton County Group, you may have expanded your chances by having several sets of the original group members.  Only testing will tell.  

Autosomal testing by should be available to the US market some time later this year.  Family Tree DNA offers their own product called Family Finder and 23 and Me calls their product Relative Finder.

Note:  As of right now, Ancestry does not offer the option of looking at raw data, which the other products do.  

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