Tuesday, November 23, 2021

DNA Research Framework 4 - Use genetic research to prove and expand your pedigree

   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 4 
The ISOGG site also has a lot of useful material refer - ISOGG Beginners' guides to genetic genealogy.  You can find earlier material relevant to earlier modules here:

Use genetic research to prove and expand your pedigree - Total cMs approach
This module focusses on using your genetic research to prove and expand your pedigree.  It considers what relationships can be 'confirmed by DNA' (including when there is no paper trail) and the Genealogical Proof Standard.  


Use genetic research to prove and expand your pedigree - 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 detailed chromosome analysis, using segment data. We use triangulated segment data to provide evidence regarding our hypotheses for cousin matching to confirm our shared ancestors.  Examining other matches in these groups can often help expand your pedigree back further generations and potentially break down brick walls.  

When using your DNA analysis to confirm relationships don't forget the requirements in the 'Genealogical Standards (GS)', there are five key elements to consider.

  • Reasonably exhaustive research
  • Complete and accurate source citations
  • Critical tests of relevant evidence through processes of analysis and correlation
  • Resolution of conflicting evidence
  • Soundly reasoned, coherently written conclusion

Most genealogical questions cannot meet the 'reasonably exhaustive research' test without the consideration of DNA evidence.  The GPS includes standards about each of the following aspects associated with DNA:

  • Planning DNA tests
  • Analysing DNA test results
  • Extent of DNA evidence
  • Sufficient verifiable data 
  • Integrating DNA and documentary evidence
  • Conclusions about genetic relationships
  • Respect for privacy rights

Remember, to confirm segments as belonging to a particular ancestor, you must ensure that three or more 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). 

When assessing likelihood of relationships it is important to:-
  • Assess the probable shared cMs for each individual match and their predicted relationship; 
  • Consider the relationship in the context of other matches who descend from the same common ancestors;
  • Use statistical analysis tools such as DNA Painter WATO (What Are The Odds) to assess probabilities for your hypotheses.  It should be noted that using total shared cMs alone will not be sufficient for distant matches as the WATO tool does not use matches below 40cMs in its underlying statistics;
  • Remember that WATO is a great visual tool to demonstrate relationships of matches beyond 3rd cousins, but it needs to be supported by additional evidence when matches are below 40cMs.  This should take the form of segment analysis including (ideally) multiple tests and triangulated groups, demonstrating that the chromosome segment has been 'walked back' through multiple generations;
  • When drawing conclusions, make sure you examine and review any conflicting evidence and document the reasons for your decision.
Mapping confirmed chromosome segment data can be a useful to assist in determining possible ancestral groups for new DNA matches and can demonstrate how confirmed segments have held up over multiple generations.   

Chromosome analysis techniques can be taken further with more advanced applications, such as phasing, inferred mapping and DNA reconstruction.  These techniques should not be attempted unless you fully understand the underlying DNA theory covered in Modules 1 and 2.





In closing

I hope you have enjoyed our chromosome analysis journey applying the DNA research methodology.  There is much to learn.  It can be challenging but equally rewarding.  It's an iterative process, requiring continuous review.  Go back over what you have learnt since module 1 and apply the methodology in practice, it will soon become second nature.

Some of our DNA mysteries may take decades to resolve, like my George Courtney - I've been at it so long I've dedicated a whole blog to him!  The key thing is to be systematic and methodical and eventually you should be able to solve your mystery.







REFERENCE MATERIAL

DNA Confirmations

Chromosome Mapping

You may also be interested in reading these blogposts relating to DNA research for my own family:

These and more can be found on 'The Genemonkey, my ancestors and DNA questions' blog @Wordpress.


Veronica Williams

Originally published: 23 November 2021
Last updated:  10 December 2023


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