My grandma's autosomal DNA match to me automatically confirms my mother?

Question

Hello,

First post..... :)

My grandmother is 97 years old and we got her to take an AncestryDNA test. I match up with her as expected. My mother has not taken a test.  AsI understand the confirmation process, I can source and "Confirm" my relationship to my grandmother with AncestryDNA predicted relationships right through my mother(even though she has not taken a test.

Is this correct? I'm just trying to make sure I do this right.

Regards

Nathan

Comments

You sound a bit new at this, so allow me to ask for this clarification. When you say your grandmother matches up on AncestryDNA "as expected", what exactly does that mean? There's no "Grandmother" category. What category did she show up in? How many cM?

I believe she should show in the "Close Family" category, with 1200cM to 2100cM, although I think I've heard of a case of a grandmother showing up in the "1st Cousin" category. Anything over 1200cM should rule out any remote possibility that she's really a biological great-aunt. I assume not that not you're worried about that, but sometimes people get surprises, and so this can show you that you do NOT have such a surprise.

Answer 1

Welcome, Nathan!

You are correct - your grandmother’s DNA results in comparison to yours can be used to confirm your relationship to her and your mother (if it’s your maternal grandmother, that is).

Here is the link to the WikiTree DNA confirmation page

Comments

Should be able to confirm if cM size is correct. e.g. in unlikely event it's half as expected, could be a great aunt.

Answer 2

Clearly your biological mother (whoever she might be) is your grandmother's biological baby.

Of course you do get those cases where the teenage daughter has a baby who is then raised by her married elder sister as her own.  If there's a possibility that your "mother" might not actually be your biological mother, even though your grandmother is right, the test hasn't eliminated that risk.

The "confirmation" rules are based on the notion that if the genealogy has gone wrong in the usual ways - somebody's wife is just a guess, or a father had 2 wives, etc - then the DNA test will not find the expected matches.

Answer 3

One exception to this generally "yes" answer is if you were adopted by your mother's sister. This does happen, but I wouldn't worry about it.