Over at the Genetic Genealogist, Blaine Bettinger has a Q&A post up about the difference between a genetic tree and a genealogical tree. The destinction is that your genealogical tree is the family tree of all your ancestors, but your genetic tree only contains those ancestors that actually left DNA to you. Just by chance, an individual may not leave any DNA to a distance descendant (like a great-great-great-grandchild), and as a result they would not appear on their descendant’s genetic tree, even though they are definitely their genealogical ancestor.
At the end of his post, Blaine asks a couple of questions that he would like to be able to answer in the future;
- At 10 generations, I have approximately 1024 ancestors (although I know there is some overlap). How many of these ancestors are part of my Genetic Tree? Is it a very small number? A surprisingly large number?
- What percentage, on average, of an individual’s genealogical tree at X generations is part of their genetic tree?
I think that I can answer those questions, or at least predict what the answers will be, using what we already know about sexual reproduction.
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