Tuesday, October 19, 2021

DNA Research Framework 3 - Combining genetic and genealogical research

  There are five parts to the DNA Research Framework:

  1. Understand DNA Basics
  2. Know what you are working with
  3. Combine genetic and genealogical research
  4. Use genetic research to prove and expand your pedigree
  5. Continuous review

Within the framework we apply a DNA research methodology to ensure we systematically and methodically review our results, to improve our productivity and success rates.

The following blog posts provide more detailed information about the DNA Research framework, applying the DNA Research Methodology and building your DNA analysis skills:

This post contains reference material relevant to Module 3 
The ISOGG site also has a lot of useful material refer - ISOGG Beginners' guides to genetic genealogy.  You can find material relevant to earlier modules here:

Combining genetic and genealogical research - Broad approach
This module covers techniques and tools to help you combine your genetic and traditional genealogy research, using your genetic data as the starting point for more targeted research.

Make sure you have maximised your findings from your AncestryDNA and have attempted to identify all your closest matches up to 3rd cousins at all DNA sites.  You should have also applied the AncestryDNA grouping process or Leeds method to identify likely match groups out to your 16 x 2nd great grandparents (where possible).  

Ideally, you want to be fairly certain that your closest matches support your pedigree out to your 2GGP's. When working with your DNA matches you need to ensure you are working from a solid base and that the pedigree you have researched, is in fact your true genetic ancestral line too.  If you have no matches on some of these lines and/or a group of unknown matches sharing large amounts of DNA with you, you may need to question whether your documented pedigree is accurate. 

The concepts associated with developing research trees from this information have been extensively covered in the AncestryDNA course and will not be covered in depth in this module.  Refer to Mossie's Musings for more information.

Recap on the key concepts from Modules 1 and 2:


Combining genetic and genealogical research - Chromosome analysis
To confirm your pedigree beyond 3rd cousins or where there is no documented paper trail  (with the exception of parent/child and sibling relationships) you need to undertake chromosome analysis, using segment data.

As a matter of course, it is recommended that any close matches at AncestryDNA who are not on any chromosome site should be approached and encouraged to upload their results to either GEDmatch, My Heritage, FamilyTreeDNA and LivingDNA (preferably all), all are free.  The following blog post can be a good one to send to your matches. I usually offer to help them interpret the results once they upload, but this depends on how critical the match is for my analysis.

In chromosome analysis our guiding principles are to:
  • Start with genetic evidence (such as known ancestral or triangulated segments and groups);
  • Limit our research to matches in that specific group for each segment area to identify the shared ancestor (increase productivity, don't go down rabbit holes based on common names etc with matches that don't triangulate);
  • Inform our research by 'clues' (such as shared matches, cross platform comparisons, cluster tools);
  • Understand patterns emerging from each triangulated group on specific ancestral lines;
  • Use each specific segment group to inform our knowledge of our genome and pedigree, pushing back segments to more distant ancestors by 'walking back the chromosome' (Module 4).

The general chromosome analysis process is:
  • Firstly, identify 'triangulated segments' on a particular chromosome of interest (between 3 matches) using 'segment triangulation' techniques (Modules 1 and 2).  Remember, by ensuring the segment triangulates with others it is validating the segment, making sure the match is 'real';
  • Next, seek to identify more people who triangulate on the same chromosome in the same segment area (between 4 or more matches), forming 'triangulated groups' (Module 2);
  • The matches in triangulated groups have all inherited a common segment of DNA, so it is 'evidence' that they all share a 'common ancestor';
  • Look for the pedigrees of your matches and try to identify what's common between those in the triangulated group, it could be names, locations, ethnicity etc.  Use that knowledge to research and identify possible common ancestors between you and your DNA match using 'tree triangulation';
  • If only limited information is provided by the match, try searching for their ancestors in other public trees. 'One World Trees' such as Wikitree, Family Search and Geni allow you to easily search for connections if your tree is already published there or search on Ancestry or My Heritage as they have the largest repositories of family trees;
  • If needed, 'develop research trees' to expand the genealogy of your matches to find the common ancestor (AncestryDNA course);
  • Once you have identified and confirmed a common ancestor for at least 3 descendants (not closely related) in the triangulated group, you can mark the segments for the others in the group to a particular ancestral line or ancestral couple.  NOTE: Other members of the group may connect via different ancestors in the line of descent, but will be connected either via a descendant or ancestor of the shared ancestors you identified for the initial 3 matches;
  • Whilst strict triangulation can only be achieved by looking at matches on the same DNA site, make sure you compare matches in the 'identical segment locations' on all DNA sites for 'bridge matches' (matches at multiple sites) as these can be additional 'clues';
  • Remember, to confirm the segment as belonging to a particular ancestor, you must ensure that all matches share an identical AND overlapping segment, i.e. a 'triangulated segment' that is 'identical by descent'.  There also needs to be sufficient genealogical distance between the matches in the group to demonstrate how the segment was passed down (i.e. not just close matches such as parent/child/siblings).  This will be covered in more depth in Module 4.
  • NOTE:  Particular care needs to be taken when dealing with endogamous communities and where there is pedigree collapse as there may be more than one shared common ancestor.  

These posts from Module 2 may be good to review:


How to decide where to start

Where you start will depend on your genealogical goals.  In my own genealogy, I am interested in confirming my pedigree back to my 5th great grandparents (6th cousin level, 254 ancestors).  I want to ensure I have the right ancestors in my tree and autosomal DNA is generally considered able to identify segments of DNA back to 5th cousins.  I find the predictions are often one generation out, hence working to 6th cousins!  I also have a couple of problematic 2nd great grandfathers.  Different strategies are needed for both.

The following suggestions are made to give you ideas about how or where to begin.  It doesn't really matter where you start, every analysis will help to identify the origins of your DNA segments.  As long as you record your findings for each segment, the historical information will help you expand your research and pedigree over time.  Chromosome Analysis is a long term endeavour - you may not find anything today but each match in the future will add more clues relating to that segment and help identify your shared ancestors.  Every small segment you identify, can lead you to more discoveries and it can be a snowball effect.

  • Do you already have 3rd cousin or closer matches where you have identified your MRCA?  Do 'one on ones' to find the segments they match on and mark those segments to the appropriate side, maternal, paternal or both (close relations, children, siblings), noting the shared ancestor or ancestral couple.
  • Matches of interest?  Do 'one on ones' for find the segments they match on, then interrogate those segment areas for likely triangulated groups who will share a 'common ancestor'.  This is the best place to start for those large unknown matches.
  • Interested in an ancestor of specific ethic origins?  Identify the ethnic origins of your ancestors using chromosome maps available at FTDNA or 23andMe and Admixture reports at GEDMatch.  Whilst not very useful for those of us with predominantly the same ethnicity, people with a specific ancestor of a very different ethnicity such as Asian, African etc often find these maps show the specific segments they inherited from that ancestor.  AncestryDNA has recently introduced its Sideview™technology, however care should be taken when using the chromosome painter ethnicity data.  It is still in BETA and from my observations the ethnicity predictions are not reliably accurate. However, Sideview™technology for allocating parental sides is proving to be remarkably accurate.


Use match information to expand your research

Don't be satisfied by just identifying the shared ancestor between you and your matches, use the information to identify more matches, discard false positive matches and expand your pedigree.
  • Known 3rd cousins or closer?  Interrogate the segment areas for these matches - everyone who also matches you and this match on the same segment will form a triangulated group and you already know your closest shared 'common ancestor'!   Do more research, aim to push 'EACH triangulated segment' back a further generation by continually reviewing the group to find more common ancestors.
  • Known maternal/paternal segments?  Remember there are two sides to every chromosome.  Once you have identified any match on a specific side, provided that 'segment area' is triangulated you can use that information to determine the other side of the chromosome.
  • Know one parent but not the other? Don't despair if you are looking for your father but can only identify matches on your mothers side.  Use known maternal matches to identify maternal segment areas, then look at all your matches on the reverse side of the chromosome, who don't match your maternal cousin.  These are likely paternal, or false positives.  
  • Have three siblings tested?  Visual Phasing is a process that can be applied to the results of 3 siblings to determine what segments each inherited from their 4 grandparents.  This is an advanced technique but can be very useful for researching more distant ancestors (Module 4).


Doing the genealogy....

No matter which way you approach DNA research, whether you stick with the broad approach or get into chromosome analysis techniques you can't escape having to do lots of traditional genealogy to bring paper trails and genetic evidence into alignment.  Both your tree and the trees of your DNA matches probably need work and don't go back far enough to find the common ancestor.  Follow these key steps:
  • Build your pedigree out as much as possible for all known lines, ideally at least to 3rd great grandparent level, preferably more (Module 1);
  • Ensure tree completeness, working from the base, aim to achieve as close to 100% at each level with 'paper' evidence for your pedigree (Module1);
  • Work with your closest DNA matches first to ensure that they are supporting your known pedigree out to 2nd Great Grandparents, if possible (Module 2);  
  • If you have no matches on some of these lines, and/or a group unknown matches sharing large amounts of DNA with you, you may need to question whether your documented pedigree is accurate, review your assumptions (Module 2);
  • Continually review and expand your known pedigree and tree completeness based on information your DNA analysis is telling you (Module 3);
  • Review pedigree information provided by the match or found by searching one of their ancestors on other pedigree sites and use it to try and identify your MRCA, particularly for all 3rd cousin and closer matches.  This is essential if you wish to be successful in chromosome analysis where we are often dealing with much smaller segment matches and more distant common ancestors (Module 3);
  • Develop research trees for your matches to help connect your two lines, common names, locations etc (AncestryDNA course);
  • Working from the base, aim to achieve DNA confirmations as close to 100% at each generation level so you know you are continuing to work from a solid base (Module 1).   This will help you 'walk back the chromosome' and build reliable chromosome maps for your autosomal DNA (Module 4);
  • Don't forget for more distant ancestors utilising Y-DNA or mtDNA analysis may be a more effective way to confirm ancestry along your patrilineal and matrilineal lines.  Given the additional costs for these tests, they are usually best utilised to confirm a hypothesis rather than used as a fishing expedition, particularly if you recruiting others to test for you.





Suggested resources:


Word of caution

* Remember segment matches of 20-30cMs and below can end up being many, many generations back.  You may not always find your common ancestor even when researching back multiple generations.

* Amassing clues from multiple triangulated groups may help you solve the puzzle over time.  For most people this a long term research exercise - and not for the fainthearted!


Suggested activities

Click this link to find activities to help you apply 'Module 3' in practice.  



Veronica Williams
Originally posted: 19 October 2021
Last updated: 10 December 2023


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