A Segment-ology CONCEPT and Thought Stimulator
Per Wikipedia: A haplotype is a group of alleles in an organism that are inherited together from a single parent, and a haplogroup is a group of similar haplotypes. Your atDNA segment from an Ancestor is likewise a group (or string) of alleles (SNPs) that is inherited from a single parent – an atDNA haplotype. The Match segments in a Triangulated Group (TG) have this same string of SNPs – they have matching shared DNA segments – and this group would then be a Haplogroup (Hg).
A Triangulated Group of segments would be a Haplogroup.
Wikipedia also notes that in human genetics, the haplogroups most commonly studied are Y-Chromosome (Y-DNA) haplogroups and mitochondrial DNA (mtDNA) haplogroups, each of which can be used to define genetic populations.
In exactly the same vein, a Triangulated Group (TG) defines a genetic population. It’s the population of descendants who carry the same segment of DNA passed down by an Ancestor. DNA test takers in this population have shared DNA segments with the same string of SNPs – they match each other!
An mtDNA Hg is often many thousands of years old (because the mtDNA rarely changes). A Y-DNA Hg is usually somewhat closer, and with a Big-Y test, is often found within a genealogical timeframe. My estimate is that an atDNA Hg (a TG) is usually 5-9 generations old – generally within a genealogical timeframe. We could argue that a TG Hg is a better tool than Y or mt. For me, it is a very good tool. In any case, each DNA Hg tool has strengths in genetic genealogy.
Note that the process of Triangulation culls out most, if not all, false shared segments. A few false Match segments (under 15cM) may slip in; but your own DNA, as the base in a TG, is true. If such an under-15cM Match is critical to you, you need to check for Triangulation with that Match segment as the base.
MUSING….
Dr. Tim Janzen – one of the earliest pioneers in atDNA (and my early mentor), has often advocated for a database of unique atDNA segments from our Ancestors. I used to think of this as a giant TG database and wonder how we would describe each TG. Now I think it would be an atDNA Haplogroup database, but still wonder how we would describe each Hg. Each segment would be unique to a specific Ancestor and would be on a specific chromosome (with start and end points). Note the chromosome could be maternal or paternal, depending on each Match’s ancestry. This segment would manifest itself in a TG, with shared segments from other descendant Matches. Each Match would likely have his or her own unique TG. These TGs taken together would represent an atDNA Hg from that Ancestor.
NB: if we can phase our data, we could actually record the SNP alleles (ACGTs) in each TG (or atDNA Hg)! Alternatively, by comparing raw DNA data among the Matches in a TG, we could probably determine the individual the SNPs. Remember your TG segment is the equivalent of phased DNA.
This post is about an atDNA Haplogroup. It’s a concept to think about. Your thoughts are welcome here.
[14B] Segment-ology: A Triangulated Group is an atDNA Haplogroup by Jim Bartlett 20230802
segment-ology 
Jim, what is the least amount of cMs you will include in a TA when looking for a TG? Some time ago, someone wrote ~15 cMs? What is the fartherest back in time, in terms of cousinship, have you found a match? My GREAT granddaughter has a match at 7th Cousin, 34 total cMs , and 34 longest segment. I have not had time to TG it, but will. It is a solid line. This match with me was 4 segments, 102 total, and 51 longest. Passing down to her, my longest segment of 51 cMs stayed strong, and she received 34 cMs. This match is her 7th Cousin.
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Caith, When I started Triangulation in 2012, I used all the segments – I believe the threshold was 7cM at the time. I continued to gather all segments over 7cM for several years, until I finally completed all TGs. Since then changed to over-10cM and recently I’ve only been adding 15cM segments – unless it’s a TG I know is distant. A TG is good for a whole ancestral line, back to the Ancestor who first formed the TG segment by combining DNA of his/her parents (thus the full segment does not go back any farther, but the smaller parent segment do).
I have several TGs for which I have several 8C Matches. I have a number of 9C to 12C Matches, in TGs, but sometimes they conflict with other, closer, MRCAs. The closer MRCA have a much higher probability of being correct; but all MRCAs in a TG must eventually add up to a preponderance of evidence. We cannot cherrypick just one MRCA – way to risky for me. In the end it’s a judgment call.
Jim
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In addition to Jim’s comment I’d like to add that nowadays 8 cM is the agreed minimum threshold amongst DNA testing companies. We have keep in mind that wherever we set the minimum threshold it will influence how many IBC vs IBD matches we’re going to get.
As Jim wrote, not IBC with 15 or more cM, surely with 7cM you can sort the IBC matches out via DNA segment triangulation. However, unless your ancestral background is from an admixture which hasn’t been tested a lot (eg. Asian, African come to my mind), you won’t need the 7 cM threshold as you will get too many DNA matches much longer already.
Especially if you’re having colonial ancestors like Jim or any group that has a lot of endogamy (eg Ashkenazi Jews). Those tend to have the most number of DNA matches and at the same time I have observed from our users that their TG’s are a bit “smaller” (meaning the difference between start and end position of the TG) vs everyone else’s TG’s.
So if you have a good lead on this match (meaning you have a much larger total centiMorgan amount with that match than your child) and also a genealogical connection than it’s well worth to go down with the cM threshold to identify a smaller match due to an unfavorable recombination event.
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Thank you for your e-mail about TGs. Like others who are interested in genetic genealogy, I have worked on mapping my atDNA for the last 10 years. Since I’m elderly, though, I would like to find a place, as you discuss, where I could make my information available, as I probably know about 50% of the ancestors with whom my DNA can be associated. An issue in providing proof is the privacy of other matches in a TG, as I haven’t known how to deal with that. In order to observe their privacy, I have begun entering a statement in my family tree on Ancestry, on records for my various ancestors, in which I list the ancestral couple, the chromosome, the segment information (beginning and end), and my Gedmatch kit number. That information provides a start, but not complete information about the DNA matches in the TG. I am also compiling TGs across FTDNA, MyHeritage, 23andMe, and Gedmatch, some of which are also in Ancestry. My tree is also on Wikitree, but the DNA information that can be posted there is limited, not specific as to chromosome and segment.
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Nedersl – I, too, have mapped a lot of my DNA back to Ancestors – it’s my main goal. Determining the TGs is a time consuming process, but within our capabilites to do it. I’ve done it. The hard part is gathering consensus data on the MRCAs for each TG – this is not necessarily “within our capabilities” – it relies on the Trees and research of others. There is a privacy factor in all of this. But with the databases of Matches now – such that we can find NPEs, and Killers and Does using the publicly available data – I think the ship has sailed. I also think your process is a good one – the info you are posting in your Tree is available at all the companies except Ancestry. I keep one spreadsheet, now over 20,000 rows of shared segment data, with info from all the companies [the TGs are mine andshould show up about the same no matter which company]. My beneficiary will get that file. But someday we will want to be able to trace medical SNPs within families, safely and securely.
Jim
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Hello Neders,
I have added in another comment how my “Your DNA family” app is addressing the privacy problem around DNA specifically.
In short, the information gathered automatically in my app about your DNA matches (such as surnames, locations and whatever else they want to share) is gathered in each triangulated group (automatically). So no need to keep information in spreadsheets that stay on private computers. Only the blood relatives, aka the DNA cousins in a specific TG can read the information, eg. all segments shared between DNA cousins, start/end position and most importantly, family tree information including automatically finding the correct MRCA’s (based on quality of family trees) and only showing the relevant branches of the family tree (where the DNA has come down from).
There’s also a private discussion forum per TG, where one can post all the information about insights, findings, family lore and proven info about the common ancestor. Again, only blood relatives can see this information. All is stored in the cloud with secure backups, accessible from anywhere in the world as long as you have internet access and a PC, Mac or Linux computer.
This link https://help.yourdna.family/hc/en-us/articles/360002562395-Who-are-we-and-why-are-we-doing-this- provides more info and you can try it out for free.
It would be indeed a pity if your years long research isn’t going to be available for future generations. Too much information is already lost when companies have taken down Rootsweb forum or Sörensen database 😦
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Great thoughts Jim, I must admit I have contemplated that in years to come our will probably be reconstructed for us. Your idea is a good way to think about it although when I consider my own genome and the vast number of TG’s I have going back, its hard to envisage how humongous the worldwide haplotree would become!
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Thanks! We can look at how large the Y and mt Trees have begun. Now spread that over all of the Ancestors out there who have passed down segments to living test taker – it boggles the mind…
Jim
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Caith – so sorry you are dealing with similar issues. I had read that before but now I can no longer remember where. I can remember things page-for-page in a book or magazine. But not on a screen. No idea why. I do have, indeed, NA in the admixture tool. Must be somewhere here in the States. But all daughters have more NA than I do! Has to mean I married someone who also has NA in their ancestry. I just keep putting one foot in front of the other – and try to do creative things to quiet my wondering brain. Take care.
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While I hadn’t heard this described quite this way, I absolutely agree with the idea. I have used specific segment details to encourage some distant cousins to test or upload beyond Ancestry for confirmations. I wonder if this concept might gain traction with (ironically) the Y-DNA project groups. I believe that actually making Y-DNA genealogically more useful depends on connection to triangulating segment groups.
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James, Thanks for your feedback. I think atDNA Hgs (TGs) are more useful than Y or mt. They actually *cover* all of your ancestry. This is a two edged sword – on the one hand it’s not limited to and all-male or all-female line, on the other hand there’s a lot of work involved. But an atDNA Hg is every bit as focused. An atDNA Hg may start out on several generations of an all-male line, but the odds are against it going very many generations. I’ve not seen a TG connected to a distant Y-DNA line, but it’s not impossible.
Jim
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James, I’d add that I have a number of TGs that I’m so sure of now, I can either tell a Match they have an Ancestor in this time and place; and/or I build their Tree back until I find it (with full confindence I will, if something’s not terribly wrong with their Tree).
Jim
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I have one person in a German genealogy forum who just wrote to me and he wants to now apply this strategy of using DNA segment triangulation to identify his all male line after his Y-DNA research didn’t lead to anything close. Ancestors comes from nowhere in 1770 but he has now identified a very small region in the north of Germany where a lot of DNA matches are coming from and that surname is also recorded.
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Yes it would be great to have a database to track all of the TGs.
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Jim, Promethease is still in business? I thought they closed down a few years ago.
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Caith – I couldn’t tell from their website. Maybe they are defunct.
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As stated in your last blog post, I’m in line with your thought on calling the unique string of alleles for a TG a haplogroup. After all, it consists of many microhaplotypes that is already used by Ancestry and 23andMe (not sure about FTDNA and MyHeritage).
People are familiar with the word haplogroup from Y-DNA and myDNA, however the actual naming of such is usually done by calling out unique variants that define those haplogroups. Which isn’t an easy way to do, hence FTDNA and Y-Tree sometimes have different SNP’s identified as variants which the other company doesn’t (yet) see as of good enough quality based on their data!
The opportunity with atDNA haplogroups (TG’s) lies in the relatively high probability to assign it to a common ancestor couple, within the genealogical timeframe.
In my experience though I haven’t seen a 5 generation common ancestor. MRCA’s yes, that’s easy to achieve but based on all the triangulated groups in our “Your DNA family” app about 60% of them have at least one MRCA identified for all TG’s.
That’s a huge difference vs mtDNA (basically impossible in my own experience even when testing the full mtDNA) and also vs Y-DNA, where again I personally did a full Y-DNA test as part of my WGS (Whole Genome Sequencing) test. My TMRCA is 2400 years before present with a Dutch, Danish and Bulgarian joining my own Northern Italian ancestor in our haplogroup. Far away from what a R1a or R1b Y-DNA tester can achieve!
You also wrote: “Each segment would be unique to a specific Ancestor and would be on a specific chromosome (with start and end points)” – please note the following comments on this statement:
– start/end positions are basically always not the exact start/end due to only a small number of SNP’s being tested in the OTC DNA tests available.
– while each segment is unique to one common ancestor it’s also possible that the same common ancestor has given you another TG’s and thus a second haplogroup.
– it’s even more likely that some of the DNA cousins of “your” TG will form another TG with some other people (not matching you) on a different locus or chromosome from the same common ancestor. That’s why it’s always good to test siblings if possible.
In regards to Dr. Tim Janzen’s idea of a atDNA Haplogroup database (also a mentor of mine), such a database exists already. My “Your DNA family” app has a 5 digit number of TG’s permanently stored safely in the cloud. Right now access to these is only available by being a DNA descendants – meaning you can only see the information and communicate with your close and distant blood relatives if you have inherited the same ancestral DNA. Any database as such always has the problem that family relationships and potential medical conditions based on unique variants have to be protected adequately.
Hope these thoughts and comments are helpful and looking forward to more discussions on this topic. Thanks for writing this blog post, Jim!
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Thanks for your insights, Andreas. Just as Y and mt are like lasers, so too an atDNA Hg (TG) is also a laser pointer along one line. Re start and end positions: there are no “signposts” in our DNA to indicate the precise location of a crossover from one ancestor’s DNA to another – even if we had WGS. And since our DNA is 99.9% the same, there will be some streatches of identical base pairs. The current DTC tests are what 30 million of us have, so thats what we need to work with. And the start and end positions are fuzzy. What is important is the relatively large bulk of a TG segment that came intact from only one Ancestor. Almost all of my TG end overlap a little (fuzzy). I just pick a spot and say thats the end of one and the start of another – unless you are looking for a “smelly cucumber” SNP near the end of a TG, it doesn’t really matter. In other words: roughly right ends is plenty good enough for genealogy – the problem is good Trees and MRCAs.
I really admire the work you’ve done in automating Triangulation and gathering good data.
Jim
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Great article! Have a question for you. I did mtDNA test and after the millions that must have been done, why do I only have a daughter as a match? Getting a brother tested now. But throwing more money at this doesn’t seem to help. Geneticists and genetic counselors have no idea. One of my mutations on the ‘Mutations’ tab is shown with an R at the end but several others have small letters at the end. (Typo?) I understand the capital R means Heteroplasmy, but even after calling FTDNA, I cannot find what those with lower case letters mean. Can you help me? Been trying to study both ancestry and dna since 2015. All the ACRONYMs are making it very difficult. All in medicine, too. Any ideas I could check on? My family has lots of health issues.
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Linda, I’m not the expert on mtDNA. A good place to noodle around is the ISOGG/Wiki – the volunteers have created a very infomative website… https://isogg.org/wiki/Wiki_Welcome_Page Maybe one of Segmentology’s readers will provide an answer.
Jim
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Did you ask FTDNA why you have only one match? What is your mtDna haplogroup that appears to be so unusual that you have only one match? Why are you testing your brother: You and your brother (if you have the same mother) will have the same mtDNA haplogroup. In 2017, I had Dr. Ann Turner in Menlo Park, California provide me with a Custom Mitochondrial DNA Report on my haplogroup, U3a1b, for a very nominal fee. Her email: dnacousins@gmail.com She should also be available to give you some clarity on your absence of mtDna matches. Please post here what she says about your absence of matches. That is so interesting! Also Roberta Estes has provided a summary of all mtDna Haplogroups. You can easily google her site and find this. DNAxplained? is her website.
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I found a link to the Roberta Estes blog, and in 2019, a woman posted that she had NO mtDna matches. Roberta opined “You must have several mutations” and she referred the lady to this link: https://dna-explained.com/2019/05/23/mitochondrial-dna-part-2-what-do-those-numbers-mean/ . This is not the link to the Haplogroup Summary Roberta has published.
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Thanks for the TIP! Will do.
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Caith – yes, I did ask FTDNA but was told to call their other company, Gene-by-Gene. My haplogroup is just T2B2B but no other subclades listed, like a lot of folks do have listed by this current year. Do I have an unusual mitochondrial mix? To your next comment: Yup – am the lady who had no matches from Roberta’s column back in 2019. Daughter matches me, of course, as do the other 2, must assume. Just checking a brother to be sure he matches me, too. If so, then we all have the same mutations. Spoke to Ann Turner back then and she said I shouldn’t worry about it – it is not pathogenic because it is in the Coding Region. So, I haven’t worried about it but it still seems odd and I know mitochondria are essential for energy production. I am one of 10 children, all of whom have quite serious health issues. Should I look up all my HVR 1&2 mutations? Could that be the answer I am looking for? I’ve known since I was 28 years old that something must be wrong with our genetic makeup. Just trying to get answers. Will take me a while to scour both the websites you and Jim have given me. Thanks for your interest.
p.s. just had a really bad fall on Sat. Sore and tired and head hurts. Will try to keep track of any comments you might leave. But I am not up to date on the latest digital stuff – especially ‘smart’ phones. 🙂
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Linda – we are distant cousins – I am T2b6a… If you want to see if you DNA indicates any health issues, I’d test at 23andMe, or google Promethease (low cost). Be careful with online companies – there are some scammers in the market now.
Jim
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Jim – thanks much! I specifically checked with 23&Me BEFORE I ordered my first test back in 2015. When I did not see the kind of issues running throughout my family, I chose to just go elsewhere for dna test. Am one of those rare folks who always looks and reads the FINE PRINT. I appreciate you allowing folks to comment. Still trying to figure this out – 8 years and counting. That’s a LOT of study but need to find answers before my grandchildren reach teenage years. Please keep up the great work you do.
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Thanks, Jim – nice that we are cousins of a sort. Have been using Promethease for as long as I’ve tested. So many ‘red boxes’ it takes me forever to try and get through them. I’ve also read 4 of the books recommended by Blaine Bettinger, I think was the author. Am a voracious reader as many have been. Those did give me general understanding but nothing specific to my issues. Am part of several groups via email, all trying to find info about our family roots. Many have families with significant health issues.
Since the advent of ‘smartphones’ it appears no one really READS anything – but they research on the internet. No one vets anything on the Internet and lots of people waste a lot of time watching those funny cat videos. (Shoulders shrugging.) We appreciate you. Europe seems to have better handle on this. States, not so much. I even joined that All of Us program of NIH. Got a dna report claiming I have wet earwax and one other thing! They were really pleased with themselves. I called them but they are only running things through computer chips. I believe we need to start demanding that we need HUMAN EYES on our Karyotypes first. See if there might be bits and parts where they shouldn’t be, etc. And look for ins/del – they have NO plans to do that. Have also noticed most dna labs are switching to newborn screening and carrier status for prospective parents. About time but wonder what that will cost and will insurance even cover it. Meanwhile….we just keep trucking 🙂 Although I am getting weary as I sit here with a blackeye traveling down my face from my fall on Sat. Somebody wish me luck, please. Gotta stop before I just fall off chair. 🙂
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Linda – absolutely wish you luck as well as good fortune in the future. I, too, am in the All of US program… I’m an engineer, so look at our DNA as a puzzle to be solved. My wife is a virologist, and had a career in NIH – she got me the child’s book: Have a Nice DNA – it was just the right level for me to get started learning DNA. A few years ago I took an on-line semester with MITx on DNA The Secret of Life taught by Prof Eric Landers who was a great teacher – and MITx is free to anyone in the world. One night my wife yelled: it’s 3am! What are you doing? My reply: I’m in a lab [virtually], folding proteins… what a hoot that course was. Sending good vibes your way! Take care.
Jim
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What a SMALL world we live in that I was able to find a post by you from so long ago and so quickly! What are the chances of that except we have been traveling in the same circles. You now know everything I know, because I still struggle with all of this. The link from Roberta I posted for you has 3 parts about mtDna, so read all 3. I believe now I had a false memory and Roberta did NOT write a blog summarizing all the mtDna haplogroups. I believe it was a summary of Native American Haplogroups. Jim, thank you for allowing this to be participatory. We appreciate the contributions you share with us.
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