View Full Version : Can you cross reference DNA test from 4 children and one parent?

07-18-2015, 03:48 AM
To determine the missing parent's genetic ancestry.

I have had my mother and two of her siblings DNA and her mother tested to determine of their late father was of German heritage. I will be testing another of her siblings soon, so I will have 4 offspring tested and 1 parent tested. I have all the GEDMATCH, Dodecad, Eurogenes, MDLP and 23andme scores of each person. The offspring appear to be predominately European, but so does their mother. How do I know if this is from their mom or dad?

I have asked this on other forums and boards but nobody was able to have an answer or even an idea

If someone can interpret these results, I will post them. I have data from my mother, two of her siblings, and her mom, could this provide a clue to their father's ancestry?

07-18-2015, 04:51 AM
Yes it could be done but it won't be perfect.

You could phase the data, i.e. line it up so you can tell which nucleotide (letter of DNA code) comes from each parent. This usually works better with more parties but with three children you should still get most of your grandfather's profile. You could then run that through Gedmatch.

Perhaps I'd use a simpler geometrical technique, at least to start, though.

You can plot where your grandmother is on a world map using the technique outlined here:


You can then plot each of their three children using the same technique.

Then draw an arrow between where your grandmother is and each of her three children, and extend the arrow as long again in the same direction as the length from your grandmother's spot to your mother's (etc.).

You will then have three new dots, with each child as far away from your grandmother's dot as this new dot.

Your grandfather ought to have come -- on average, and roughly -- from inside the triangle created by these three new dots.

07-18-2015, 10:16 PM

I have been working on showing how siblings match their segments to each of their grandparents by figuring out which parent gave each of them the crossover border to each segment. The segments can then be compared to an Admixture calculation as shown in the picture.

I apologize for the busy slide. You have to stack a lot of comparisons, one on top of the other.

One cousin was available to confirm a segment that triangulates with a relative of Dad's maternal side.

A browser that permits fully identical (double matching) between at least three siblings is needed for the mapping.


12-05-2015, 05:35 AM
How do you do that? I have four siblings genotyped and their mother from this family