Earlier this week I made a free transfer of two of my grandsons' atDNA results from MyHeritage to Family Tree DNA (FTDNA). Since the lab testing for MyHeritage is done in FTDNA's Houston lab, this is a fairly seamless process. As with any new procedure there were a couple of minor obstacles. FTDNA had yet to upgrade the Autosomal Transfers entry icon to mention that MyHeritage kits could also be transferred.
I was then able to continue my learning process which had begun a couple of weeks ago when I received access to these results at MyHeritage. My previous posts demonstrated that grandchildren do not inherit equal amounts of atDNA from each grandparent although it appears that each set of grandparents contribute 50%. To review this post click here.
I then made a follow-up post in which I demonstrated that these variances of amounts of atDNA inherited by a grandchild can alter ethnic predictions between full siblings. To review this post click here. If these changes sometimes can be observed within only two generations, we can only imagine how they could be skewed over five or six generations of compounded random inheritance. This explains a big part of the differences between ethnicity predictions of full siblings.
On to the Chromosome Browser
Using Family Finder's Chromosome Browser tool, I examined the contributions each set of grandparents made to each of the two grandsons. This process allowed me to visualize things I sort of knew intellectually:
- Each set of grandparents combined to pass down 50% of the grandchild's atDNA but the grandparents within each set did not contribute equal amounts;
- Each grandparent's contribution to full siblings differs -- sometimes in measurable amounts;
- There really are two different strands of atDNA inherited by children -- one from the father and one from the mother;
- We can visualize the "crossovers" on the paternal and on the maternal strand of atDNA inherited by the grandchildren and thereby trace which part of the grandchild's atDNA was inherited from each grandparent; and
- Grandsons do not inherit any xDNA from their paternal grandparents.
Maternal grandparent contribution
In this image the atDNA contribution of the paternal grandparents are charted for grandson #2. Note than no xDNA was inherited from the paternal grandparents through the child's father. In this case about 26% of the grandson's atDNA was paternal grandfather (represented by the orange bars). About 24% was inherited from the paternal grandmother (represented by the bright blue bars).
One other item of interest to report came out of this exercise. Family Finder identified more Ashkenazi DNA from both grandsons than did MyHeritage. One grandson appears to have inherited about 22% of his atDNA from his primarily Ashkenazi grandfather. No other grandparents have been shown to have any Ashkenazi inheritance. Family Finder Identified about 18% of this grandson's atDNA to be Ashkenazi.
The other grandson appears to have inherited about 26% of his atDNA from that Grandfather. Family Finder identified about 21% of this grandson's atDNA to be of Ashkenazi origin.
MyHeritage had identified the first grandson to have 10.8% Ashkenazi and the second one to have 17.5%.