A Segment-ology TIDBIT
The old saying: How do you eat an elephant? One bite at a time. We can, and should, apply this advice to Triangulated Groups and Chromosome Mapping. Take it a TG/segment at a time.
These days, the Matches are pouring in, and it’s easy to get overloaded with data. So I’m setting two goals:
- Form one new TG every day
- Communicate with the Matches in a TG each day
Each person’s objectives and available time are different, so set the timeframe to suit your own situation (every other day, each week or whatever). The point is to put a goal and plan in place.
There are about 400 TGs spread over my 45 chromosomes. So at one-a-day, it would be March 2018 before I could form every TG for my Dad (I’m just getting started on his chromosome map). But by then this long ignored project would be done; and his map would provide extremely valuable information for my chromosome map.
And if I send out a small group email (average 10 Matches) to the most significant Matches in a TG every day, it will be March 2018 before I focus on every TG. But two good things will happen: 1) I will have focused on every TG, and worked on the Common Ancestor; and 2) For about every 10-20 emails/messages I send out, I determine a new Common Ancestor. So by March 2018 I’ll have another 200 or so Common Ancestors. [NB: Each CA is not necessarily the correct genetic link for the TG, but they are all genealogy cousins and provide important clues in our quest to “walk the ancestor back” and/or obtain multiple agreements on the TG CA.]
In other words, we reap what we sow – we get a percentage return on the communications we send to Matches – the more we send, the more we get in return.
Again, everyone’s situation is different. All I’m suggesting is to set a goal, and schedule some time for TGs and chromosome mapping. Take a periodic bite out of the atDNA elephant!
[22H] Segment-ology: One Segment at a Time TIDBIT by Jim Bartlett 20170218
segment-ology 
Thanks for this bllog post
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Caith, I need to add that a segment from an ancestor is on either your paternal or maternal chromosome – not both, not a mixture – it’s all paternal or maternal. Somewhere back in time, that segment will be a composite from two distant ancestors – the segments get smaller and smaller as we go back many generations – but they are not a composite of your parents’ DNA.
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Caith, re: John SMITH. How do you “know” that John SMITH is the Common Ancestor for that segment? Did you “walk the ancestor back” to John SMITH or find multiple Matches in that TG who all agree on John SMITH? Have you, somehow, ruled out any other ancestral line for that TG?
If you have just one 7C who shares John SMITH as a Common Ancestor with you – that is just one clue – it is not proof.
Now don’t get me wrong, I record all the Common Ancestors I can find with each Match (sometimes I’m related to a Match multiple ways). But I have many Triangulated Groups with conflicting Common Ancestors: one Match says John SMITH, another says Bob JONES, another says Jane MILLER. This is not uncommon with Colonial American ancestry. The DNA segment represented by the TG comes from a specific ancestor, down a specific path, to you. The genealogy puzzle is to find sufficient evidence that points to one ancestor and one path. One distant CA is not sufficient.
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Caith, Right now, I think GEDmatch is the only company that lets you compare any two Matches to each other. If you have access to multiple kits (at FTDNA or 23andMe) you can do comparisons with them – for instance I admin my maternal uncle’s kit at FTDNA, so I can directly check to see if both of us share the same segment with a single Match.
At 23andMe, old version, we used to be able to compare Matches to each other. I have many such Triangulations recorded in my spreadsheet, even though this feature is now gone. However, 23andMe does have a new feature in their in common with list – they note a Yes when an ICW Match also has an overlapping segment. I’ve tested this on over a thousand shared segments, and only found one anomaly. So I now take the 23andMe Yes as a Triangulation.
At FTDNA if you have two Matches with overlapping segments AND one is on the other’s ICW list with you, they turn out to be in the same TG over 95 percent of the time. When this is the case among 4 or 5 Matches, it’s virtually 100 percent.
Remember, every shared segment has to be either: IBD on your paternal chromosome; or IBD on your maternal chromsome; or not IBD (false, almost always under 15cM). So the over 15cM shared segments “have” to Triangulate on one side or the other. The under 15cM shared segments should Triangulate or be tagged as not IBD. However, many of these smaller (under 15cM) shared segments are going to be from fairly distant Ancestors.
My go-to site is GEDmatch, but I group all my Match-segments at 23andMe and FTDNA also, using the above techniques.
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Is the following statement correct?
A TG can only be proven at Gedmatch because only at Gedmatch can you do a one-to-one comparison to prove each person in the TG is related to each other person which is essential to proving a TG.
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Jim, Somewhere in blog comments some time ago you posted something and I think the light only went on today. You mentioned how each person’s segment analysis is specific to them (or something along those lines). So, does that mean if I triangulate with other people on say, MY Chr 1 and we identify a CA based on trees. If I were looking at THEIR triangulation results, we may not triangulate on their Chr 1, but we would match on an entirely different Chr? So they don’t need to know what Chr they match with on my study, but only the length of the largest segment and the total amount (to help us determine distance)? If that is correct, would we triangulate with the same people on their different Chr? All I know is I am writing emails and getting matches (or not; which I think NPE or one of us has a bad paper trail). In that case what do you do?
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Barbara, A shared segment with a Match is only the overlapping part of a segment you each got from the Common Ancestor. The full segment you got from the ancestor is the full TG (usually made up of several/many shared segments with different Matches. Each Match absolutely got a segment from that Ancestor, too, but each Match would probably build a different TG around their own segment. So each Match in a TG has a segment from the Common Ancestor at least as big as the shared segment with you (on the same chromosome).
Test this with a close cousin – compare the cousin with each of the Matches in your TG. They will have an overlapping TG which often extends in one direction or another from yours. This means the cousin got a segment from the Ancestor which is different only in the start and end locations (from your TG segment), but on the same chromosome, and roughly the same location, but usually not exactly the same start, end, cM and SNPs. So “different” only in the sense of “not exactly the same”. It helps me to think of an ancestor passing down his/her DNA to their descendants, and each one getting some.
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Just confirming , that if I have a triangulation with my Common Ancestor, John Smith, on Chromo 1, with segment 2,000,000 – 3,000,000, that is the segment that I can ASSIGN to John Smith? Of course, realizing that the chromo and segment have two sides, matra and patra, since the chromo and segment are a reflection/mixture of both parents.
And, I do understand, if the above match is from my father’s side; then I would have another match on my mother’s side on the same chromo and segment.
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With Colonial Ancestry I often get conflicting CAs with Matches in a TG. I record them all, and look for consensus as more and more Matches come in. And I hope for a 3C or 4C and/or 5C to eventually show up in the TG – to “walk the ancestor back”. At some point the correct CA will emerge, and we can work on the children and grand children of that CA and then go back out to all the Matches again with that info. Often they’ll recognize that they do in fact descend from that Ancestor. NB: our Matches with shared segments under 15cM (or smaller than the TG) may we’ll descend from a somewhat more distant ancestor – ancestral to the TG CA – who may we’ll be beyond a genealogical timeframe. I realize that we’ll probably never know how some Matches tie in (their TG would usually be fairly small!! if we worked it out at GEDmatch – or if more folks did chromosome mapping)
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Two more items: 1. Each TG is a segment from an Ancestor to you – usually made up from shared segments from Matches. 2. If you compare each Match to each other Match, and graph the results, you’ll usually get a somewhat larger group. In general, this represents the full segment the Ancestor started with, and you can pick out of this larger Group the full segment passed down to each Match. The main point is that each of us is not the “center of the universe”. We each have our own niche, and got our own slice of the pie. Sometimes this bigger picture (from the Ancestor’s perspective) gives us a better feel as to how we fit in.
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Barbara, I think I’ve found an NPE in my Tree – I actually changed the Ancestor in my Tree, and I’m waiting to see if I get any better results with that.
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I should add that at one point I bit the bullet and Triangulated virtually all of my shared segments. This created almost 400 TGs, almost all were adjacent to each other from one end of each chromosome to the other. Now, all new Matches very neatly “fit” into existing TGs. So now the quest is to find MRCAs for as many Matches in each TG as possible – starting with the closest/easiest Matches first. The goal is to get 4 or more who all agree on the same CA; and/or to walk the ancestor back with closer cousins in the TG (not always possible).
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Could you expand a bit on how you find the CA – even if wrong, as you say? I have looked at a few TG’s but only in one do I have a guess as to who the MRCA couple is, for the other we don’t know, although we have a common surname in the group. How can you narrow down the generation or relationship, when the charts show such a broad range as to “distance” – could be a X.greatparent or a X-cousinXremoved… I feel like a dog chasing my tail.
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Well you mention a dog chasing his tail – and this work is dog-work. It’s hard and tedious. I have looked at every Tree I can get my hands on – thousands of them – and I’ve clicked out to 8th to 12th cousin range (at Ancestry that’s the 3 set of pedigree boxes) for virtually every one of them. Even when I find a Common Ancestor, I keep reviewing the Tree until I’ve seen it all. I often find more than one Common Ancestor. I have some TGs with 7 or 8 different Common Ancestors – clearly they cannot all be right – the DNA segment comes down one specific line. But which one?? We have to continue to research the Trees in each TG to find the Common Ancestor that will fit all the Matches.
Narrowing down the generation can only be done with fairly close Matches. As you note the 7-15cM shared segments could come from a very wide range of Ancestors – don’t even try to pin it down! One “trick” you can use is to only use a higher thereshold – say 10cM or 15cM or 20cM. You’ll get fewer TGs but the MRCAs will tend to be closer.
Jim
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Jim, you and I tackle this the same way. I also sometimes find 5 or more CAs in a tree, and also match with 5 segments at times (and these are not cousin marriages).
My mode of operation is to find 3 or more people with the same Tree CA and then try to do a TG. It is easy up to 4th cousin; but thereafter very difficult. Since DNA does not lie, but paper sometimes does, and because many trees are just PLAIN WRONG, this proves some of the mistakes in trees (probably including my own).
How those people at Ancestry who have DNA plastered all over their trees think that a tree match is a dna match without proving it with segment matching defies all COMMON SENSE and is beyond belief. And Ancestry does nothing to disabuse them of this notion…………
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AncestryDNA, by not showing us the shared segment(s), actually encourages and promotes this kind of false (fake?) genetic genealogy. This kind of practice actually winds up in “proofs” of incorrect ancestry.
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Hi Jim. To be honest, I’m very overwhelmed. I ran my DNA analysis through AncestryDNA, and while the results aren’t too scientific, I can definitely interpret them better than some of the science-heavy stuff I’ve found on GEDmatch, etc.
Here’s the thing. I’m adopted. I do know my biological mother, but, she is adopted too and knows nothing about her biological family. What’s more, she does not want to tell me who my biological father is.
So, after a lifetime of looking and wondering, I’ve hit dead end after dead end. Do you have any advice or resources you’d recommend? I’m sure you get these kinds of messages a lot, and I’m sure you find it tedious to respond, so any counsel you might offer would be great.
-TIm McCauley
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Tim,
Most adoptees are looking for a very close Match, in order to get a toe-hold on their ancestry. Most of us giving advice, will recommend testing at all 3 companies and uploading to GEDmatch. You can transfer (copy) your DNA data to http://www.familytreeDNA for a small fee; and you can upload (copy) it to http://www.GEDmatch.com for free.You never know where that close Match might test. The next step is to log on and work with the folks at http://www.DNAadoption.com – they have a process and it’s been very successful. What’s more they have folks who are dedicated to helping adoptees.
As you might gather from this blog, I am a fan of Triangulation as it groups your Matches by ancestral lines. But you’ll still have the issue of trying to find a close relative to work with.
Good luck – another key ingredient,
Jim
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Tim, if you have not already done it, you should join DNA Detectives on FB. They are a group of new and seasoned genetic genealogists (many of them are adopted themselves) and they teach others proven methods of identifying biological family. The triangulation method that Jim teaches is a FANTASTIC additional tool that will give you connections that will get you going in the right direction. I had to read Jim’s blog from his first post and move forward. I had been trying so hard to understand what people were talking about. I was still in the dark. As I read Jim’s posts IN ORDER it was like someone playing with a dimmer switch in my brain. As soon as I thought I understood and was grasping the concept the light would dim again. I can be a bit slow on the uptake. Now I am working with the light on (most of the time). It continues to get brighter each day as I work with results of Gedmatch Tier 1 tools. (With a $10 donation that gives access to the tools on Tier 1, you can obtain enough information to keep you busy for a year.) If you’ve done the test at AncestryDNA there is a method that exploits the system to assist in finding bio family. DNA Detectives teaches people willing to do the work how to use this method called, Mirror Tree. They will also help you “read” your results. Jim is right, sometimes finding a “close” match is the key. You never know when that will happen. With the tremendous influx this past Christmas (holiday gifts of DNA tests set all time high records) still being processed, new results are being posted daily. Search for the blog post, “DNA and Genealogy: I Am So Confused What Do I Do Next?” The best advice— don’t ever give up!
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What is Duffys Null and is it “sticky”? When you down load your raw data to GEDmatch, what are you downloading, the A, C G and T’s or DYs?
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Autosomal DNA looks at specific SNPs (not repeats like Y-DNA). So your raw results are hundreds of thousands of specific SNPs. For each one the SNPs, the test determines the allele (an A, C, G, or T) for each parent. Since we don’t know if it’s on the maternal or paternal side, there are only 10 possibilities for a SNP: AA AC AG AT CC CG CT GG GT AND TT. It’s this table of two values at each SNP that is downloaded and then uploaded to GEDmatch
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Thank you Jim. Especially in these trying days your message was timely.
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Peggy, I’m with you – atDNA is a handy refuse
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For all of us, mapping our DNA could be done more efficiently and effectively if we had a way to record online the results of our mapping. Something like: On Chromosome 14, from Beginning Segment X to Ending Segment Y, kit numbers A, B, and C match. The common ancestor for kit numbers A, B, and C is: John Jones, born 1852, died 1928. This registry could be Boolean searchable by kit number and chromosome. And by the name and birth date of the common ancestor.
Yes, I agree with the previous post. Nonexistent trees, lack of response, and incorrect trees are slowing down work on mapping.
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I am finding that as more people form TGs and map, we help each other with just this info. It’s like the end-play of a jigsaw puzzle – with fewer and fewer options. I am now able to provide specific information to my Matches about the probable line and segment info of other Matches. With more and more frequency, I’m able to give an ancestor and the Match has it in their Tree. As some people get a lot of their maps filled in, they will be gold to many of their new, and old, Matches.
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I know it’s not what you are asking for Sandra, but I have found genome mate pro a fantastic way to keep me organised on a personal level and to focus on one chromosome at a time. As a result always looking at TGs. Wikitree is also a useful place to record the results against the common ancestor so some of that information and GEDmatch IDs get out there., via DNA confirmations and sourcing the genetic match. Not as automated as you are thinking about, but a start!!
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Gedmatch now has it set up so you can link to a specific person on the Gedcoms. I think it would be great if the geniuses at Gedmatch added a space where the chromosome addresses could be added. What do you think Jim?
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I think the shared segment info is unique to you and your Match, in general. As such it would be better to track this info in your own personal spreadsheet, where it can also be compared with other shared segments which might not be on GEDmatch.
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Is there a way to do this with TGs, which don’t necessarily have the same exact shared segment? I have read speculation that eventually it might be possible to take a DNA test, enter it into a registry, and come up with a genetic family tree, including the names that are in the associated paper family tree, even with unknowns designated. If that could be done, doesn’t there have to be a first step, associating paper trees with DNA matches, in a registry? We are just beginning this process, but how do we pass on the knowledge we are developing?
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It is exciting to work with TGs. Lack of response is a problem; and I wonder if some of the trees are wrong when I do not find success when I think I should……….
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Faith, I agree it’s exciting (and hard work). And yes, many of our Matches have no Trees, very small Trees, incorrect Trees, etc. We have to accept that, and send out more emails and messages to new Matches. And I cycle through old Matches every year or so – and sometimes get a BINGO! the second or third try. I think we are all learning and improving. Some (many?) Matches drop out – we must move on – the new Matches are coming in faster than ever!
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Couldn’t agree more Jim! It’s all about chipping away!. Although it is very time consuming and disheartening when silence is the stern reply. But then often something new comes out of the blue and you’re off again!
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Veronica, that’s why I point out that you have to sow a lot of seeds (emails and messages) to reap a few responses and even fewer MRCAs. But there is a return on this investment, and it will get better as we fill in our maps.
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