Chromosome Browser, common surname on #19

[manoss]

I've looked through previous threads, but did not find this topic discussed exactly. Apologies if I missed the answer elsewhere.

I have a common surname on 2 matches. We're Ashkenazi Jews from Eastern Europe. I compared them in Chromosome Browswer, & we all overlap at #19 but at no other chromosome. The attached pdf shows the overlap in green highlight. The RJW person also matches me at 2 other segments on #19.

Isthis single instance of overlap significant to investigate further between the 3 of us? We do not have the same towns in common, only the surname. RJW has stated that JLR is also a match on their results.

[Javelin]

RJW has stated that JLR is also a match on their results.

There are two sides to each autosome, so it's important to know if your two matches also match each other on this same block, or if they match each other but somewhere else?

If it's a three-way match on the same block you all have a common ancestor. If it's not, you might or might not have a common ancestor, but your block is coming from a different one of your parents in each case.

[manoss]

There are two sides to each autosome, so it's important to know if your two matches also match each other on this same block

Thanks Javelin. So if I can clarify - even though I show all three of us overlapping on Chr #19, I need to find out if they show the same overlap?

My assumption is that they will see the same overlap on Chromosome 19. But it sounds like that may not be the case, and I'm not sure how that could be.

I mean - since I show all three of us overlapping these blocks, and given that they also share a FF match, would not they show the exact same overlap, just from a different perspective?

[mkdexter]

Your answer is - because it is possible that your maternal DNA overlaps to one person and your paternal DNA overlaps to the other person. You can't tell which one unless you've tested your parents too. The tests show either one in the chromosome browser, sometimes both.

If the other two people match each other then your chances go up as to the fact the three of you are related by the same common ancestor.

If you had a parent tested and your parent matched both of them also then you would basically know for sure that the other two and yourself and your parent are all related by the same ancestor.

Being the segments shared are small it becomes more difficult to be sure of this and it becomes harder to determine who that ancestor is but its a start.

Good luck!

[manoss]

Chromsome #19

Your answer is - because it is possible that your maternal DNA overlaps to one person and your paternal DNA overlaps to the other person. You can't tell which one unless you've tested your parents too.

Ah, thanks, now I get it. As far as my personal situation, I have the fortune of my maternal Irish Catholic/English WASP roots; and my paternal Ashkenazi Jewish background. So for me, I'm fairly certain, based on the surname, that this is the Jewish paternal side.

But, I'm not the only mixed breed in this dog show. And the same situation applies to my matches.

[Javelin]

mkdexter has explained it well for you. I have one example of this already, where two longish matches overlap but come from different sides:

-one person's segment matches in that spot to my father, but not to his father, my grandfather
-the other's does not match my father or grandfather, but matches my maternal second cousin

So one match is from my father's mother, while the other is through my mother's mother (who was the sister of my cousin's grandfather). And now if anyone else matches me on that segment, I should be able to work out the link much more easily.