Part 539b – Brunhammer Doherty Genealogy – Comparing 23andMe Autosomal DNA Results

28 June 2011

Evening, and still no AC,

Well an examination of 23andMe results is the discussion. We decided to use two Brunhammer candidates to see if we could understand exactly what 23andMe is trying to do. The candidates are brother and sister of the Brunhammer clan, and as we know, both have the same parents, Eugene John and Myrtle Frances Gertrude (née Doherty) Brunhammer.

The first results are included with the Ancestry Painting. The Ancestry Painting “feature takes a look at the more recent heritage of your chromosomes, segment by segment. It identified the pre-colonial home continent – Africa, Asia or Europe… of DNA along the 22 chromosomes that are inherited from both parents.

This does not include the sex chromosomes. These are the autosomes. AB’s autosome inheritance is identified as >99% Europe and <1% Africa. KBF’s are identified as 100% Europe. Somewhere in time a minute indication on a segment of AB’s chromosome #4, there is an ancestor who may have passed on the information that he or she may have originated somewhere in Africa. This is that <1% indicator.

The next 23andMe tool is the Compare Genes function. Accordingly 23andMe will take the Genome-Wide Comparison of 928693 SNPs (Single-Nucleotide Polymorphisms) and compare them between clients to determine the percent similarity. AB’s and KBF’s similarity is observed at 86.22%.

As you can see in the top diagram, comparing the top 1 to the bottom 2 there is one SNP that is different. Of the over 928693 SNPs of ABs and KBFs that were compared approximately 800719 SNPs are similar. This is a very high correlation. This is a comparison of all 22 pairs of autosomal chromosomes excepting the sex chromosomes. This definitely proves that there is a chance that AB and KBF are siblings. And of course we know that AB and KBF are siblings…same parents, same house, same city, same state. The question is what would be the similarity percentage between the other brothers and sisters?

The next 23andMe offered tool is Relative Finder. The results between AB and KBF are: 1. Predicted Relationship – Sibling; 2. % DNA shared – 46.14%; and 3. # Shared Segments – 46. And exactly what do these mean?

Well, number 1, the Predicted Relationship – Sibling, I am glad to say is correct. This certainly puts to rest the old tales that AB was told by his older siblings that he was “adopted from the lower part of Jersey” and that he was “really was from China”. At least 232ndMe got the Sibling Relationship right. The next closest 23andMe Predicted Relationship to AB in the possible 868 Results from the database is a gentleman who may be a 4th Cousin.

The next sets of results are the % DNA Shared – 46.14%. And this means? 23andMe defines this as “The percentage of identical DNA shared between you and a potential relative.” The 23andMe table summarizes the average % of DNA Shared for different types of cousins.

Based on date provided by on RootsWeb and the Degrees of Relation and Number of Genes Shared. Parents, siblings, children, and fraternal twins may share about 50% of their DNA with each other. Bingo on AB and KBF at 46.14%.

Number 3 states that the number of DNA Segments shared between AB and KBF is 46. Here is a visual plot as presented by 23andMe.

Well a cM or CentiMorgan, according to 23andME, is a measure of how easily a particular segment recombines. And this means? Well that’s the next discussion.




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