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GATA GACC! DNA and Genetic Genealogy Today

This lecture covers the basics of DNA testing, Y-DNA testing for males, mitochondrial DNA testing for males and females, and how to find DNA projects and testing companies. An introduction to analysis of the DNA test results is given.

Sample genealogical research problems are used to explain how DNA can be used by genealogists.



In the last ten years the use of DNA testing for genealogical purposes has expanded enormously. In the last year or two the science has advanced to the point where autosomal DNA (DNA other than just the Y chromosome and mitochondrial DNA) can contribute to knowledge of our family history. Aside from what you can learn today about your family history, there are two other great reasons to take a genealogical DNA test:
  1. to ensure your DNA results will be available to your children, grandchildren, nieces or nephews as new discoveries are made in the coming years, and
  2. to contribute to the advancement of the science so those new discoveries can be made more quickly.


Your genealogical goal will determine which DNA test you need and which person in your family should take the test. In general:
  • Y-DNA tests trace the lineage from father to son and follow a surname in western society; Y-DNA tests can only be performed on a male subject, but a woman can recruit a male relative to take the test; the test can be performed on a male of any generation of the lineage without significantly affecting the test results
  • mitochondrial or mtDNA tests trace the lineage from mother to child; mtDNA tests can be performed on a male or female subject, but only a woman passes mtDNA to the next generation; the test can be performed on a person of any generation of the lineage without significantly affecting the test results
  • autosomal DNA tests (Family Finder at Family Tree DNA) trace the DNA from all ancestors, not only the direct paternal and direct maternal lines; the test can be performed on male or female subjects; whenever possible the eldest person in a lineage should be tested to see the maximum number of matches


This pedigree chart shows which ancestors each type of DNA is inherited from.
DNA pedigree

This chart shows which descendants inherit Y-DNA and mtDNA from an ancestral couple. Autosomal DNA is inherited by all descendants, whether male or female. (Squares represent males, circles represent females.)
DNA inheritance


See Debbie's Maternal Lines: Using Mitochondrial DNA (mtDNA) presentation for mtDNA information.

See Debbie's Paternal Lines: Using Y-DNA presentation for Y-DNA information.

See Debbie's Going Nuclear: DNA Discoveries to Trace All Lines of Descent presentation for Autosomal DNA (atDNA) information.

See Debbie's List of DNA Reference Works for a selected bibliography of genetic genealogy references online and in print.




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CG, Certified Genealogist, CGL, and Certified Genealogical Lecturer are service marks of the Board for Certification of Genealogists, used under license by board certificants after periodic evaluation.



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