I have just updated the Outline of Segmentology. This is located in the black bar in the header of every page – just click it. The posts over the years have jumped around; the Outline tries to put the titles in some order – sort of like a Table of Contents. Each one is hyperlinked to the blogpost. This Outline provides an easy way to scan through the topics and blogposts and navigate to the ones that interest you. Don’t forget to read the comments and questions for each blogpost – they often contain additional information.
[00] Segment-ology: Segmentology Outline Updated by Jim Bartlett 20230604
segment-ology 
Jim, I’m very curious as to why you have stressed a 20 cM minimum threshold in your discussion of triangulating at MyHeritage? Is that particular to the MH algorithm or would that apply to other testing companies as well. I thought that a 15 cM threshold virtually assured us of IBD segments. Mike Crowder
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Mike
MH has two versions of 20cM – one for shared segments and one for TGs. They impute data (SNPS) which means some of their false segments may be above 15cM. My 20cM is just an arbitrary threshold. 30cM would involve roughly half as many total Matches, and fewer TGs. Adjust the threshold for your own threshold of tedious work. You can always add more Matches with a lower threshold, and make slight adjustments to your TGs later, based on the additional data more Matches bring. Jim
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Jim, Thank you so much for updating the ‘Outline’. Thank you also for all of your very informative blog posts. I am relatively new to ‘Genetic Genealogy’. I am trying to learn as much as possible, and your posts have been extremely helpful in that learning process. It seems the more I learn … the more questions I have. Mike Crowder
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Hey Jim, Thank you so much for updating the ‘Outline’! I also want to thank you for all of your very informative blog posts! I am a beginner with ‘Genetic Genealogy’, but am committed to learning as much as possible. It seems as if the more I learn … the more questions I have.
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macro; Thanks for your feedback. And please feel free to ask questions in the comments – we all usually benefit from the discussion. Jim
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Thank you! I always appreciate help with navigation.
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Thanks for your feedback Melissa – I try to tackle the many aspects of genetic genealogy in multiple ways… Jim
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What a thoughtful thing for you to do. I am certain that I will find it extremely useful. Thank you.
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Barbara, Thanks for your encouraging comment – it’s my pleasure; and it helps me keep track of what I’ve already posted (many more posts in progress… Jim
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Hi, This looks great. Love reading your articles. Having them in an organized layout is wonderful. I would love to be able to triangulate my matches and figure out what segment came from which ancestor.Debbie
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Thanks for your positive feedback.
I think the best way to start with segment Triangulation, is to test or upload at MyHeritage; then download the spreadsheet with all of your shared DNA segments in it; sort it by cMs and delete all segments under 20cM; then sort by Chr and Start and check each Match’s Shared Match list for the TG Icon and note in the spreadsheet which ones match each other. It is work, but I believe it’s well worth it. Jim
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Hi Jim.Sounds like a plan. Is that how you worked through your matches to get all the triangulated groups and traced back to your ancestors?Debbie
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Debbie,
When I started segment Triangularion, it was the “old days” haha. I was one of the first to work on full genone Triangulated Groups – about 2012. It was a slog. My Heritage wasn’t around then, nor did any of the companies have good tools. Many times at FamilyTreeDNA, I had to send an email to two Matches who overlapped with me and ask them if they overlapped each other. Most didn’t reply… GEDmatch was a help, but only a small percentage of my Matches had uploaded to GEDmatch. It took me about 4 years to get a rough outline, and then I did a “forced march” through every Match-segment – which took another year. Today, it is much easier at MyHeritage – their computers tell you the segments that Triangulate. Just WOW! Today, I’d start at MyHeritage, and limit to over-20cM segments – sort on Chr and start – and just walk down the list (skip over any that are not easily determined – revisit them at the end). This gives you a framework. Remember: the crossover points between TGs are *fixed* in *your* DNA – once you have them, they are the same at any of the other companies – your DNA (and it’s crossover points) are the same no matter which company tests your DNA.
Finding the Common Ancestor is a different chapter – this is all about the genealogy. Sadly, the companies which provide segment data, don’t have much in the way of good Trees and genealogy tools and records. Ancestry has the best, but no segment info. So finding the MRCA is not a slam dunk. I have thousands, but there are many more needed. Jim
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Hi Jim,I tried different methods over the years. I get a clue here, something over there. Always liked hearing that you made breakthroughs with your research, and had so many triangulated groups. I started phasing my Chromosomes. Manage to get a few figured out. So that will help with the cross over points and knowing which grandparent the segments are from. I have to finish the rest of the chromosomes and try to work triangulated groups again. Have to read through your articles. If I remember correctly you started going into smaller matches once you made it through the higher amounts. This is good news, because I don’t have many in the higher amounts, especially on sites with a chromosome browser. I know more chance of false matches. Just need the time to work on it. I know takes a while.Debbie
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Debbie. I fiddled with mine for years, and then just did a “forced march” down the list of shared segments. Today, I’d use only >20cM segments at MyHeritage. In the spreadsheet I had about 10 narrow, blank columns to the right of the segment data, and I’d highlight those that Triangulated in one of the columns. Once a segment row is highlighted, you don’t have to review that segment again. So start with one Match in a spreadsheet on one monitor (or window) and look at the MH Shared Segments on the other monitor, go down the list in MH and highlight per the TG Icons. Once you’ve formed all the TGs (and then you have to determine if each group is Paternal or Maternal) that frame work is yours forever (some ends might shift slightly, and when you use smaller segments and large TG might split into two. But the basic framework mirrors your DNA – so it’s the same at GEDmatch, 23andMe and FTDNA. Jim
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Hi Jim,Sounds good. Do you use google sheets or excel for your spreadsheets? Today I spent some time reading through your blog going down the outline you made. I made it to Anatomy of a TG. I thought I would read through your posts before starting on my matches. This way I can ask you questions along the way and make notes.Debbie
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I’ve used Excel for over 20 years.
Jim BartlettSent from my iPhone
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Gary – I’ve often thought about a book/booklet, but it would be outdated before printing. I’m thinking out a “living book” of some type that I could just continue editing and adding to. Fun for me, but a PITA for folks to re-read regularly…
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Thanks, Jim. This saves a lot of time and trouble keeping track of the back copies of your posts.
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