AT DNA Triangulation?

montgo

Another query from a DNA newbie.

I have a good match with my known cousin, Philip (112cMs) and I have a 30cMs match with Joe, Philip has just 11cMs with Joe. However on Ch8, we have an overlapping segment (Joe's segment size is only 4cMs). If this is triangulation, can I assume that Joe connects with us (me & Philip) through our most recent common ancestors ie our gggrandparents, John & Mary? Or is this an incorrect assumption?

Many tks,

pinkypinky

My best understanding is that it is possibly right but since it's a very small match, it could be just noise.

Paddy Waldron's talk at Genetic Genealogy explains this sort of thing very well. It's not up on their Youtube yet but should be soon.

montgo

Thanks Pinky, I will look out for Paddy's talk.

montgo

Any update on the DNA Atlas project?

KildareFan

I haven't dipped a toe in the DNA pool yet - don't want to shatter my childhood fantasy that I was kidnapped at birth and my real father was Leonard Cohen....

montgo

montgo

Not a DNA triangulation query this time:).

I've just noticed while I share 112 cMs with my above mentioned cousin on Gedmatch, we only share 55cMs on Ancestry!!!

How can there be such a difference?

dubhthach

Calculator effect? You have to recall that basically it's down to how good their software is. Software can often have bugs in it.

dubhthach

montgo wrote: »

Any update on the DNA Atlas project?

Supposedly it's in process of peer review, so hopefully 2017 for first paper to be published. In general though whenever they give talks about it they nearly want people to sign an NDA

montgo

dubhthach wrote: »

Calculator effect? You have to recall that basically it's down to how good their software is. Software can often have bugs in it.

Many thanks for replying. I had noticed smallish differences before between Ancestry & Gedmatch results but never 50+cMs diff.

Another 3rd cousin, same MRAs, has 120+cMs with Philip while I share only 18cMs. Even considering that we should generally inherit 50% of our DNA from each parent, 25% from each grandparent, etc, would this difference be taken as normal?

tkx

dubhthach

montgo wrote: »

Many thanks for replying. I had noticed smallish differences before between Ancestry & Gedmatch results but never 50+cMs diff.

Another 3rd cousin, same MRAs, has 120+cMs with Philip while I share only 18cMs. Even considering that we should generally inherit 50% of our DNA from each parent, 25% from each grandparent, etc, would this difference be taken as normal?

tkx

I will admit that my own interest is specifically around Y-DNA and ancient DNA when it comes to autosomes, so I havn't really paid attention to when it comes to shared levels of cMs in a genealogical timeperiod.

What I would say though is process of inheriting 50% from each parent is random, so it could simply be that by random luck you didn't inherit the same chunk of chromosome