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Matings To determine how reliable AncestryByDNA™ 2.5 was for measuring admixture levels we can also computationally perform matings between simulated individuals. By the laws of genetics, the ancestry percentages for offspring should be predictable given knowledge of the percentages of the parents. To plot the distribution of admixture levels in offspring from a family tree with 3 Europeans and one homogeneous African, we used the allele frequencies to randomly generate one 100% Western sub-Saharan African and 3 100% European grandparents. We then mated the simulated African grandparent with one of the simulated European grandparents and the other two simulated European grandparents to generate a F1 generation (a simulated mom and a dad). These two people would be expected to show approx 50:50 and 100. We then mated this simulated mom and dad pair to generate a simulated F2 offspring (i.e., a person taking the AncestryByDNA™ test). We repeated this 100 times to generate 100 F2 individuals. By the law of genetics (independent assortment) we expect each offspring has their own unique percentage, because the inheritance of chromosomes is a random process and some offspring get more or less African markers in common with the African population. However, the average offspring would be expected to show 25% African and 75% European BGA (note that these simulated individuals are not “related” since the grandparents are randomly selected from the simulated population). We can see from the distribution of BGA percentages in the simulated F2 that the average offspring exhibits about 25-26% African ancestry, as expected, in addition some offspring show more or less admixture, which is also expected.
Below, we performed the same experiment using a simulated East Asian and 3 simulated European grandparents. Again, the average F2 offspring exhibits the expected level of East Asian admixture.
Below, we performed the same experiment using a simulated Native American and 3 simulated European grandparents. Again, the average F2 offspring exhibits the expected level of Native American admixture. Experiments using other types of combinations show the similar results.
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