Genealogical DNA Tests – Let the Hard Work Begin …

The holidays are nearly over. This is a race against time.

Here I am, sandbags set aside, fires out and a mere fortnight before the back-to-school panic sets in for our household. I’m way behind with my family history objectives and hopefully my father’s DNA test is to complete in three days time.  I’m just not organised yet.

First of all, there were the usual new matches trickling in each week which I’ve scarcely even looked at.  They are all distant, they’ll wait.  More exciting stuff is afoot.

My mother’s Family Finder test dropped quietly in with 563 matches – way more than I have and way way more than my son has. First lesson learned – every single generation makes a huge difference with matches.  Test the earlier generation. Everyone has said this but now I’ve seen the difference with my own eyes.

Second lesson is a corollary of the first but I just hadn’t twigged.  My mother, genetically, is quite different to myself.  I thought she’d have half of what I had, only bigger, stronger, more defined and the rest would be less useful.  What she has is a whole lot of different stuff with strong cousin matches.  I can’t view her results in comparison to mine.  I can go the other way, yes – look at a matching segment from her and see where I have inherited only three quarters of that segment – but the reverse doesn’t work as easily.  The segment boundaries have to come from her kit.  My portion is fused with the neighbouring portions and the cutoff point isn’t clear.

Perhaps this is the nature of the Australian colonial population.  We came from distinct endogamous regions so even if the families did not mix in Australia, they were cousins back in the homeland.

In my mother’s match list are one daughter, one grandson and one third cousin, known and verified.  It’s a nice beginning.

Next are twenty 2nd-4th cousin matches.  TWENTY!  I was very pleased to have four, but my mother has twenty.  If I ever get beyond these it will be a miracle.

The verified third cousin aside, I had three which I was hoping to resolve via my mother’s test.  One turns out to be on my father’s side.  This one may be further clarified when his test comes in.  This leaves two as yet unidentified 2nd-4th cousin matches from my own list which also match my mother.  These are the ones I am writing about today.

In an earlier blog I gave these matches fake names for easier identification.  I called one adoptee cousin Cecilia and the unresponsive cousin Jennifer.  In my own match list Jennifer was in second place and Cecilia in fourth place.  In my mother’s list, Jennifer is in seventh place and Cecilia is in tenth.

Jennifer is simple.  My mother matches a total 57.6cM with her.  I match 47.65cM.  The matching segments are consistent.  It looks quite genuine and behaves predictably.  This is not a long term resilient segment passed down unchanged from practically the middle ages, as some look to be.  Jennifer is a genuine medium-range cousin..  It would be nice to know where she fits. It looks as if she connects on my mother’s paternal side and I’m guessing she is a fourth cousin to my mother.

Cecilia is interesting and complex.  Her match with my mother is 54.35 cM and her match with me is 48.85 cM.  Some of it makes sense where I inherited a lesser portion of my mother’s segments.  However, I match Cecilia on three chromosomes for about 4cM each where my mother doesn’t.  Her 54.35 cM match is only about 70% in line with mine.  The rest of my match with her, therefore, either is Identical by State (coincidentally the same) or is inherited through my father.  I’ll find out in a few days.

Which brings me to the third lesson learned from my mother’s DNA test results.  You cannot assume the size of an inherited segment from just one match.

In my mind, a segment is a block of data inherited from a forebear.  It came unbroken.  If I have a large segment match, it seemed quite clear that the segment came from our common ancestor. I fully understood that I might match via two distinct MRCA’s, but somehow I assumed those segments would be distinct from each other.  Would have lines between them, for instance.  Something like this where on chromosome 5 there are two portions near each other but not touching.  The dark blue is my mother’s 100% and the orange is the bit where Cecilia matches her:

Yes, that was a mad conclusion and certainly not one I had consciously come to.  Here is one chromosome of Cecilia’s compared to myself (top) and to my mother (bottom):

A small portion of this match came from my mother.  A larger portion – sitting seamlessly beside it – did not.

This has taught me a whole lot about my matches in general.  I was operating under a sort of binary methodology – it would be one way or the other.  But if DNA comes from both sides, then a 3rd cousin match might really be a 6th cousin match on both sides.  What a challenge for anyone trying to use DNA testing to break down brick walls.  You really need to improve the odds by increasing the identifiable portions before taking off into ancient times on a forebear hunt.  Once I can identify which DNA came from which grandparent, that’s when I should be looking further back.  This means testing cousins!  I wonder if I have any cousins who would like to be tested?

In the meantime, I’m going back to the start – mapping my chromosome to identify which grandparent gave me which segment.  Learning to walk before I try to run – and that’s one lesson I never seem to learn!