Foundations in DNA 3 of 5: Understanding Autosomal DNA

In this engaging installment of the “Foundations in DNA” webinar series, renowned genetic genealogist Blaine Bettinger demystifies autosomal DNA testing and its critical role in family history research. Geared toward genealogists of all levels, this session lays a strong foundation in understanding how autosomal DNA is inherited, how it’s used in cousin matching and ethnicity estimates, and why these concepts matter when interpreting test results. Bettinger’s clear explanations and illustrative examples make complex genetic principles approachable, helping attendees navigate the intricacies of modern DNA testing with confidence and curiosity.

• Autosomal DNA Inheritance is Complex and Variable: Unlike Y-DNA or mitochondrial DNA, autosomal DNA is inherited in a random, recombined fashion from both parents. This means each person inherits a different mix of DNA from their grandparents and earlier ancestors, making every individual’s genetic profile unique—even among siblings. Understanding this randomness is key to interpreting centimorgan values and estimating relationships accurately.
• Not All Relatives Share Detectable DNA: While close relatives (up to second cousins) almost always share detectable DNA, more distant relationships—such as fourth or fifth cousins—may not appear in test results at all. This is due to the random nature of inheritance and the decreasing likelihood of shared DNA over generations. Therefore, genealogists must balance genetic evidence with traditional records and remain open to the possibility of non-genetic connections.
• Testing with Multiple Companies Expands Research Potential: Bettinger strongly advocates testing across the “big four” autosomal DNA companies—AncestryDNA, 23andMe, MyHeritage, and FamilyTreeDNA—to maximize match opportunities. Each company has different databases, tools, and ethnicity reference panels, offering unique advantages for uncovering relatives and refining ancestral origins. Strategic testing can significantly enhance the depth and breadth of genealogical discoveries.

And don’t forget to explore the comprehensive syllabus and related resources available through Legacy Family Tree Webinars. These materials provide additional context, tools, and references to support your ongoing education in genetic genealogy. Dive in and take your DNA research to the next level!