Establishing my Great-Grandparents DNA Profile

Well, parts of it anyway. 🙂
This week, the 23andMe DNA Roots Into the Future results came back for one of my mother’s paternal 1st cousins.  A great advantage of her having done the test is that I can now begin to establish segments of my mother’s DNA that comes from her paternal grandparents,  Lewis & Lucinda (Lennon) Robinson, whom Cousin C and my mother have as their Most Recent Common Ancestor (MRCA).
“Cousin C” shares 10.5% and 28 segments of DNA with my mother.  All 28 of those segments come from Lewis & Lucinda.  Additionally, Cousin C shares some DNA segments with my mother’s brother that she does not have in common with my mother (11.2% and 32 segments).    Because the sharing with my mother and uncle are not 100% overlapping, this means even more segments from the great-grandparental units.
In the image below the DNA Cousin C shares with my mother is marked with green; the DNA she shares with my uncle is marked in blue.

This means that as I sort through my mother’s Relative Finder matches, if someone matches both her and Cousin C – then that person is related to us through Lewis & Lucinda and will thus help me narrow which branch to focus the search on.  As I have started to tabulate these shared segments into my analysis spreadsheet I have already identified a few individuals who I can now narrow our search for our MRCA to that branch of my tree.
And also of interest, I have parts of DNA of a set of my 2nd great-grandparents, Andrew & Gracy (Bullock) McNair on my mother’s side since a 3rd cousin of hers, for whom Andrew & Gracy are the MRCA, has also had his testing completed.  On my father’s side, I’ve got DNA segments attributed to ancestors of mine even more generations back that these — how cool is that?
I really need for one of the DNA testing companies to add the tagging capability I’ve described on my blog in the past — it would be so helpful!