DNA Triangulation and Wiki

+13 votes
336 views
I posted before about a match to my known 4th cousin and was told I need to triangulate, not use FTDNA 'In Common With', so I am now on GEDMATCH and my known 4th cousin and I match with the same (there are several) people that we had in common on FTDNA. We have compared trees to a few of the others and we understand where it is we share our most recent common ancestor however, only myself and my originally known 4th cousin are on Wiki......does that mean that I need to create profile for the other cousins? And then do their tree/ancestry to where it connects with  the tree shared by myself and my 4th cousin? A couple I have asked already and they are not intertested in joining, they are on others sites.
in Genealogy Help by Anonymous Anonymous G2G6 Mach 1 (16.1k points)
retagged by Darlene Athey-Hill

What Gedmatch Ids do you have= 
Anonymous Anonymous has T726788 

I send you a message.

2 Answers

+6 votes
Will you clarify what you mean about matching several people both on FTDNA and on Gedmatch?  Are you all sharing the same segment on the same chromosome, or are you all just 'in common with' one another? In order for it to be a triangulated group, you all need to share the same segment on the same chromosome.  Also, what is the size of the segment you are sharing?

You are correct that, if your cousins aren't interested in participating at Wikitree, you will need to create profiles (for the ones that you know their date or year of birth) for the descendants of your common ancestors down to your known cousin.
by Darlene Athey-Hill G2G6 Pilot (369k points)
Thanks Darlene, that is what I thought and I was hoping not to have to do that :/ I wish they would take an interest in Wiki.

Some of the matches are on the same chromosome and the lengths vary.
If you already know this, fine, but just in case you don't know.... you only have a triangulated group if you share a common segment with two or more others.  You might share a 14 cM segment, let's say from 18-32 on chromosome 1, with your known 4th cousin. You might share a 9 cM segment from 21-30 on chromosome 1 with another cousin. You need to do a 1 to 1 comparison on the two cousins to be sure that it's on the same chromosome (you have two chromosome 1s, one from each of your parents). Without doing the 1 to 1 comparison between the two cousins, you wouldn't know if they were matching on the same chromosome 1...
Thanks Darlene, and yes that makes sense. On another note......I also have another two matches (not in common with the ones I was discussing above) however they are siblings, so my understanding is that I need to find 1 other match that matches them as well as me (same chromosomes and decent length segments) before I can triangulate?

Also Darlene, from my first example

Known 4th compared to me and new match (matches us both and we know now where he comes into our shared line)

Chr 5

Match ID Type Name Matching segments on Chromosome 5 Overlap with previous match
1 F2 new match 88844181 - 101616094 (9.589 cM) New Root
2 F2 known4th 89041320 - 101510882 (9.30399 cM) 89041320 - 101510882


  Chr 6

Match ID Type Name Matching segments on Chromosome 6 Overlap with previous match
1 F2 4th 75593660 - 96218093 (13.9305 cM) New Root
2 F2 new 30958170 - 42246511 (14.0275 cM) New Root

 Chr 11

Match ID Type Name Matching segments on Chromosome 11 Overlap with previous match
1 F2 4th 33752989 - 61635091 (19.1927 cM) New Root
2 F2 new 132564807 - 134436845 (3.787 cM) New Root

Done one to one (Me to known 4th then me to new match)

4th

Chr Start Location End Location Centimorgans (cM) SNPs
5 89,041,320 101,510,882 9.3 2,073
6 75,593,660 96,218,093 13.9 4,052
7 140,018 11,206,772 19.7 2,909
11 33,752,989 61,635,091 19.2 5,318

Largest segment = 19.7 cM
Total of segments > 7 cM = 62.1 cM
Estimated number of generations to MRCA = 3.9

652733 SNPs used for this comparison.

New

Chr Start Location End Location Centimorgans (cM) SNPs
3 36,496,268 55,909,455 14.0 4,077
4 115,076,076 130,594,600 9.6 2,780
5 88,844,181 101,616,094 9.6 2,167
6 30,958,170 42,246,511 14.0 5,951
13 17,956,717 25,542,465 15.0 2,371

Largest segment = 15.0 cM
Total of segments > 7 cM = 62.2 cM
Estimated number of generations to MRCA = 3.9

672039 SNPs used for this comparison.

So does that look right so far?

 

and new to 4th cousin

 

Chr Start Location End Location Centimorgans (cM) SNPs
5 86,231,405 107,218,417 15.2 3,474
8 62,051,023 86,527,569 20.6 4,848

Largest segment = 20.6 cM
Total of segments > 7 cM = 35.8 cM
Estimated number of generations to MRCA = 4.3

When I look at it, we share a match on the 5 chromosome......

 

If I'm reading it correctly, you have a triangulated group on chromosome 5.  You've got a 9.6 cM segment on chr. 5 with the new match and a 9.3 cM segment on chr. 5 with your known 4th cousin.  They share a larger segment on chr.5 (15.2 cM from 86-107).  But for the triangulated group, you're sharing a segment from 88-101 on chromosome 5 (abbreviated #s on start & end location).

As to your other question with the siblings,you are correct that you need another person for a triangulated match, since they're siblings.  The same would be true if you were matching a mother and daughter.  You'd need an 'unrelated' third party to match them and you.
Thank you again Darlene, this part I understand much easier than I did trying to up load my raw DNA to GEDmatch.
Do the 4th cousin and this new cousin match each other in the same places where you match with each of them? (That's needed for triangulation.)
Yes they do. See Darlene's answer above.
+4 votes

Hi Anon, In case you missed it, I wrote how I use auDNA test matches recently.  http://www.wikitree.com/g2g/229558/how-do-you-use-your-audna-test-on-wikitree?

by Kitty Smith G2G6 Pilot (525k points)
Thank you Kitty. I do know the connection, and will start to add the new matches branch (thank goodness it is not to long and not complicated) when I have time. I still would like to know if I have the correct info for our triangulation above though, and if it is correct how would I word it to add to my profile after I make the new branch?

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