One Segment at a Time

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:

  1. Form one new TG every day
  2. 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

14 thoughts on “One Segment at a Time

  1. 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!


    • 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.

      Liked by 2 people

  2. 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……….


    • 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!


  3. 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.


    • 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.


    • 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!!


      • 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?


      • 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.


      • 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?


  4. 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?


    • 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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