Monday, February 05, 2018

Comparing Shared DNA from paternal 2C1Rs

In one of my earlier blog post, I'd promised to do a comparison of paternal 2C1R(2nd Cousins once removed).    Below I am comparing segments that I and my siblings share with a paternal 2C1R.  This cousin is the 2nd Cousin of my Dad and our Most Recent Common Ancestor Couple is my Cook/Putman 2nd Great Grandparents.  The Cook/Putman couple are his Great Grandparents

Look at the difference in total that my sister and I share with our 2C1R as compared to what our brother shares.  If my brother had been the only one who tested we would have missed out on identifying over half of the DNA which was received via the Cook/Putman connection.  I should mention that this paternal 2C1R(who is kin to us thru his paternal lines) is also a maternal 4C1R(thru his Mom's McElroy/Shropshire lines )  He shares no matching DNA with my mother at the 5cMs/500SNPs threshold. 

Since our Dad passed on before we began testing we can't know what he would have had in common with this cousin other than looking at what all of his children have in common with this match.  Still, there may have been segments that my Dad did not pass on to any of us.  The next best thing we can do is test his sister and see what segments she shares.

By testing our Paternal Aunt who is a 2nd Cousin to this match we are able to identify 7 additional segments with this Cook/Putman cousin.  These are segments which neither I or my siblings received and are noted by the blue arrows in the above image.

This next set of 2C1R are children of a paternal 2nd Cousin.  They are half siblings to each other.  Our Most Recent Common Ancestor Couple is my Cook/King Great Grandparents.  The Cook/King couple is their 2nd Great Grandparents

There seems to be pretty good variation in the Chromosomes which I share and those which my two siblings share with each of these 2C1R  Thankfully I didn't stop at just testing myself as I seem to have less shared segments. Let's see how my Aunt compares.  She is their 1C2R.

It looks like our Aunt has most of the same segments in common with these two who are her 1C2R.  We were still able to identify a chromosome segment that my siblings nor myself had gotten which came from the Cook/King couple(noted by the dark blue arrow)  Also we were able to pick up more cMs on about 5 other segments which are marked with the lighter blue arrow.

There is a good deal of randomness in the heritance of DNA once you are back past your parents.  Test 2nd Cousins, Aunts/Uncles, and siblings. 2nd Cousins are gold mines.  They will really help you sort out the information you need in order to identify your matches.  Too, if you expect to be able to identify 3rd and 4th cousins you need to have a well-researched tree and know the descendants of your 2nd and 3rd Great Grandparents. 

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