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Sunday, January 1, 2023

The evidence is within us! Autosomal DNA analysis: Part 1


Test results from the genetic company arrive in your email inbox and the journey begins. Sometimes unexpected and unnerving results turn our world upside down, but more often we are amazed that a lab was able to link us to locations and living relatives who share segments of ancestral DNA. It is a profound moment. Genealogists currently use consumer DNA testing companies to confirm their documented family tree or use the new methods of genetic genealogy to break down brick walls and push back their pedigree charts.  

There are currently three tests consumers can take that measure different parts of the cells.   


Test #1: Autosomal (AtDNA) is the test advertised on TV.  That type of DNA is a mix in every individual with 50% from each parent.  Siblings have similar, but unique combinations of the parent DNA.  Half of the genes are inherited from the mother and half from the father.  That does not mean the tester received copies of all maternal genes representing all her ancestry, it means that randomly upon conception the tester received half of what maternal genes were available.  Siblings inherited half of their maternal genes, but a different selection.  The other half of maternal genetics was lost to the tester but may appear in sections of his siblings or in smaller amounts in cousins who got DNA from grandparents.  Because of the inheritance pattern and the loss over generations of DNA from ancestors, this test is best used to find or confirm ancestors for the past 4-5 generations. Submitted samples from the oldest relatives are therefore most helpful in the analysis of results as they were closest to the ancestors further back in time.


The AtDNA results can be used in several ways.


  1.  Lab results can predict your ethnicity and ancient origins. Interesting, but not always 100% accurate.  Their analysis is based on each company’s test group in countries around the world which are compared by the computer to your results.  Every company has different analyses and various sizes of sample populations for comparison.

  2.  Matching test results with others who test can help solve lineage questions.  Most of the match lists with other testers sharing some of your DNA will be unknown relatives, but some may have family photos, documents, or other information that will help illustrate or push back family lines.  

Test #2: Mitochondrial (MtDNA) testing is for men or women to show what we inherit from our mothers.  Women pass it on to all their children, so men have their mom’s MtDNA, but do not pass it to children. This might help with maternal ancestry.                     



Test #3: Y-DNA is tested only done with male subjects as females received two X chromosomes, but males received XY. Follows the male line for many generations.  This information could possibly help with paternal ancestry.

Once the results arrive from the test company there are steps for best practices suggested by professional genealogists, the Board for Certification of Genealogists, and the International Society of Genetic Genealogy who are all concerned with privacy issues, professional and ethical use of results and teaches genealogists how to use results in effective analysis.