What are DNA Charts?

DNA charts and tables are automatically generated by determining the most recent common ancestors found in your database for your configured DNA tester and all their configured DNA matches. The tables will include a summary of the details derived from those matches, and will link to the DNA charts for each of those ancestors. Each chart will link up every DNA match for whom that ancestor is the most recent as well. For a detailed look at how to create DNA charts checkout Configuring Ancestor DNA Charts.

Ancestor DNA Charts
Ancestor DNA Charts

By now most of us have taken a DNA test with one of the major testing companies, all of which provide the tester with a list of DNA matches, those other testers to whom the tester is related. In the details for each relationship are found the total segment length of shared DNA, the number of matching segments, and sometimes, the length of the largest segment. This is all the information necessary to approximate the degree of kinship between a DNA tester and their DNA match. Knowing something about a DNA match's pedigree can further determine the distribution of possible relationships.

Gigatrees supports adding all of your <DNA> match details from the various testing companies to your configuration. You do not need to modify your GEDCOM file or genealogy database to make use of this feature. Preferably, your database will include the ancestors for both your DNA tester and your DNA match, up to and including the most recent common ancestor (MRCA). This information can be determined by your research directly, or copied from Ancestry's ThruLines™ or MyHeritage's Theory of Family Relativity™. Based on your DNA match details, Gigatrees will determine the highest probable relationship and automatically determine the MRCA from your GEDCOM data (if provided). It will also derive the relationship between the DNA tester and the DNA match, compare the results to the most probable relationship determined, and then create a DNA relatives table showing all your DNA match relationships (including kinship offsets, half relationships, double cousins, and pedigree collapses), the derived relationship, the probability and relaibility of that relationship and a suggested relationship if a more probable relationship is found.

DNA Relatives Table
DNA Relatives Table

The table will be linked on the DNA tester's profile page as a tab when individual profile pages are enabled, as well as linked from the menu. If multiple testers are configured, the menu will link to an index page listing each. Note that a derived relationship with the highest probability, unless they are a parent or child, will never show a probability value of 100%, it will always be less, even when it is the highest probability. Gigatrees adds a reliability column in the table to provide additional assurances. Finally, the table will also link to the MRCA's ancestor DNA chart, showing a graphical display of their relationship.

In addition to the DNA relative table, Gigatrees will also create a DNA ancestors table listing each MRCA for the DNA tester, the number of DNA relatives who share the MRCA as their most recent common ancestor as well, the maximum and minimum shared DNA length from the list of matches and a column indicating which side of the family the MRCA is from, i.e. father's side or mother's side. The MRCA's name is linked to the same ancestor DNA chart. The table will also be linked on DNA tester's profile page as a tab, as well as from the menu.

DNA Ancestors Table
DNA Ancestors Table

One of the goals of adding DNA match data to Gigatrees should be to supplement your existing documentation to derive a more accurate parental reliability assessment. When DNA matches are used to validate a DNA tester's MRCA, their reliability assessment can optionally be set to "proven", which is the highest relibility available. The reliability assessment will be shown for all parental assocications as you can see here in the following generation list.

Ancestor List
Ancestor List

Gigatrees's goal is not to predict unknown relationships, though it can be used for that, but it will only provide the probability for the most likely relationship. Brit Nicholson's Orogen Weighted Relationship Predictor and Jonny Perl's Shared CM Tool can be used to provide a more detailed analysis.

It is usually best to add your shared match data in the percent of total chromosome length rather than in centimorgans (cM) when that information is provided with a high enough resolution. Testing companies, like MyHeritage, which do provide the percent value, do not do so to a very high resolution, so in this case it may be beter to use centimorgans. When centiomorgans are used, Gigatrees will calculate the percent value based on the testing company listed. This is necessary because each testing company uses a different total chromosome length (See Brit's article on The Overused Centimorgan for more information). When no testing company is included, Ancestry is assumed. The following values for the total chromosome length will be used by default:

Total Chromosome Length
6768 cM
6950 cM
7000 cM
7074 cM
7174 cM

As you can see, DNA charts pack of lot of information into just a few pages and are a valuable assest to add to your documentation and proof arguments.