DNA ~ Grandparents and Grandsons

Earlier this year, both of my sons agreed to having their DNA tested. Because my autosomal DNA is primarily British Isles with a little bit of Scandinavia and West and Central Europe, and my husband's DNA is about 96% Ashkenazi, it makes it interesting to view our children's admixture (or ethnicity) results.

I always like to make it clear that with ethnicity results that they are estimates and can vary dramatically depending on the reference populations that the DNA is compared with, as well as the regional definitions used by the DNA testing companies.

In fact, where the majority of my DNA is British Isles with 8% West and Central Europe (according to FamilyTreeDNA), Son#1 shows 48% of West and Central Europe and no British Isles. Son#2 shows 43% West and Central Europe and 11% British Isles. Neither show Scandinavia. (This may have to do with the fact that my first DNA test was with AncestryDNA (in November 2011) and I transferred the raw data to FTDNA, and my sons tested directly with FTDNA.)

Because I have tested three of their four grandparents (my father, who would have been fascinated with all of this, died in 1993), I was able to determine how much DNA each son inherited from each grandparent. (See my parents-in-law ethnicity results as of April 2016 at One Jewish Family's DNA Ethnicity Results; since then, they have changed slightly as FTDNA has updated their database.)

At FamilyTreeDNA, each of my children are reported to share 3,384 cM with each of me and my husband. Grandchildren are expected to inherit about 25% of each grandparent's DNA, so about 1,692 cM. However, due to recombination in each generation, it rarely comes out that way.

For those who are unfamiliar with the term: cM refers to centiMorgan, a unit of measurement when referring to shared DNA.

The following numbers come from FamilyTreeDNA. To create the pie charts, I mathematically adjusted for the fact that due to endogamy in Ashkenazi Jewish populations, their paternal grandparents, Anita and Harry, share some DNA.

Son#1:
shares 1,682 cM of DNA with Harry
shares 1,784 cM of DNA with Anita
shares 1,385 cM of DNA with Margot
theoretically would share 1,999 cM of DNA with Charles

Son#2:
shares 1,800 cM of DNA with Harry
shares 1,646 cM of DNA with Anita
shares 2,006 cM of DNA with Margot
theoretically would share 1,378 cM of DNA with Charles

And of course, their match lists are easy to phase (separate out by parent) because those with Ashkenazi DNA match via my husband and those with British, Scandinavian, or Western European DNA match via me.