Help With Grouping Matches

[Vi5]

Hi to all.

I'm just trying to learn the basics of DNA matching using a chromosome browser and would like help with the following:

1. I have a confirmed match and know the MRCA with yellow. Can I now add the other matches to this couple?

2.  If I find a match (that is not any of those in the diagram) and they were to match with the small green isolated match, would this mean they could be tagged to the same MRCA?

I hope this rambing makes sense 
Vi

[pughcd]

Hi Vi5,

If you are looking for help understanding shared and overlapping segments it is worth reading around the subject. Blaine Bettinger's blog is an ideal starting point.

https://thegeneticgenealogist.com/2016/06/19/a-triangulation-intervention/

[CorleyMiller]

Hi Vi5,

My view would be that you can’t make that assumption.

When matches triangulate they most likely do share a common ancestor but may not necessarily all share the same MRCA with yourself.

For example, I have two matches A and B who triangulate.
Match A descends from my great grandparents and therefore they are my MRCA with A.
Match B descends from my great grandfather’s brother, which makes my MRCA with B, my great great grandparents.

Hope that helps

[Biggles50]

Who are you using for the chromosome browsing?

These site will also help in your learning

https://www.familyhistoryfanatics.com/

https://forums.gedmatch.com/BB/index.php

[Vi5]

@ pughcd  - Thank you, I will check that out.

@ CorleyMiller  - Thank you for your explanation. Am I correct in assuming then, that as the matches on C1 are on my paternal grandfather's mother's line, I can at least allocate all matches on C1 to that line but not necessarily that ancestral couple?

@ Biggles50 - Thank you. I am using the chromosome browser on My Heritage and pasting to DNA Painter. On and off over the years I have watched and read almost all I can find on the subject. Unfortunately somehow I just cannot click with it. I don't have many known or high cM matches which doesn't help.

[CorleyMiller]

Yes, but not all matches on your paternal C1, it’s only triangulated matches that are most likely part of that particular line. For matches at other locations along paternal C1 you’d have to work out separately which paternal line they belong to.

Have you tried the new cM Explainer feature that MH have introduced? There is a tick box option to see the probabilities of where the MRCA could be with each match.

[Vi5]

Further to my previous question. In the image, 1,2,4 and 5 triangulate and are on my paternal line. As 4 does not triangulate, could this mean it will probably be on my maternal line?

[CorleyMiller]

In my experience I'd say it was probable but never 100% certain.

I have an example:
Fig 1a shows two of my maternal matches that triangulate

Fig 1b adds a third match that happens to be the child of the orange match, triangulation disappears.
If I didn't know that relationship existed, I could easily have assumed that the third match was paternal.

I'd check the shared matches of your no 4 match, particularly those with the triangulation symbol, to see if there are any clues as to which side they're on.

[Vi5]

Thank you. I will check the matches for clues as suggested.