Thursday, February 01, 2018

A DNA match who shares 3 different kinship paths

Comparing Grandparent--Mom--Child
I have a new match from Ancestry who has uploaded to GEDmatch.  She has been on my Ancestry match list for a while.  She is kin on my Mom's side thru 3 different lines.
The closest is thru my Maternal Grandfather's Luna & Pittman line.
The other 2 lines are my Maternal Grandmother's Hale/Elzie & Hitchcock/Fleming lines.
While we have the Hale Hitchcock connection in one union the match has separate lines that go back to our common ancestors.  This means we have the potential for sharing segments from both my MGF and my MGM.  Fortunately, I have a sister and a brother who have both taken autosomal tests and I hope visual phasing will help to identify the ancestors responsible for these segments.

Let's look at how they were passed down from my Mom to me and from me to my daughter.

[image edited ch 13 info was inadvertenly placed in the ch 18 row in the Daughter table in my initial post and I've corrected the image so that it is now showing in the correct row.]

Comparing Matching segments passed to 3 children
We can also add my siblings to the mix and observe how Mom passed the segments to
3 of her children.  I have 2 brothers who haven't tested and neither of them has children so whatever they have inherited will not be passed.

Looking at the Amount of shared DNA for each of the 3 siblings and the match
Looking at amounts she is my 2C1R, 4C & 4C1R.
It's not as easy as adding up the avg amounts for all of those relationships and getting a guesstimate on what she should share because 10% of cousins do not match once you get to the 3rd Cousin range.  When you get to 4th cousin level it is about 50%.  Let's see how they compare 2C1R, 4C & 4C1R average amounts added together are 123+35+28 = 186 cMs.  With me and my siblings, she matches highest with my brother at 161.5 cMs...with me at 150.1 cMs and my sister at 91.7 cMs.  There probably won't be many if any Hitchcock/Fleming segments and only a little more likely are the Hale/Elzie segments.  The majority of the segments are likely Luna/Pittman segments.  I feel that since 2 of the relationships were a 4th cousin and beyond, that the multiple relationships really didn't play that big of a part in inflating the amount of shared DNA.

Looking at these comparisons it's easy to see how over a few generations the segments from those ancestors can dwindle away.   I see something odd on Chromosome 18 where my brother's segment is 36.8 cMs which is considerably more than my Mom's 21.8 cMs.  Maybe an identical by chance portion.

Ancestry doesn't include the X in any of its results.  You can, however, download your raw data and upload to GEDmatch.  Let's take a look at how my Mom, siblings, daughter and myself compare to this match on the X chromosome.  Remember the inheritance pattern of the X Chromosome.(<---see additional="" at="" bettinger="" blaine="" blog="" info="" p="" s="">This inheritance pattern only applies to segment matches on the X and not on the other 22 chromosomes which can come from ANY of the ancestors who you have in common.

Notice the 3.07 cM segment that my sister shares on the X that Mom doesn't share with this match.   Also, there is a 5.57 cM segment that my sister and I both share.which isn't shared with Mom.  Likely false positive segments.

Eventually, maybe I will be able to "assign" the segments to specific ancestors or ancestor couples at least.  I have a feeling this is going to take a good while.

If you are looking for tools to use for DNA analysis, I have a listing of my favorite tools, blogs and educational sites on my DNA Tools and Reference page.

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