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How does an Ancestry DNA test work?

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Quick Answer

Ancestry DNA takes a small sample of saliva and uses autosomal testing to find both paternal and maternal ancestors. Most genetic testing focuses on the Y-chromosomes, which are male genetic markers, or on the mitochondrial DNA passed down through females. Individuals of both sexes can take the Ancestry DNA test.

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Full Answer

Autosomal DNA testing looks at chromosomes directly inherited from a person's parents. When a child is conceived, it inherits an equal amount of DNA from each parent. Going back another generation, each person inherits roughly 25 percent of her DNA from each grandparent. This halving process continues for each generation of ancestors. By the time a line reaches the great-great grandparent's generation, a person's DNA has roughly 6.25 percent from each of 16 individuals.

After being collected, the saliva sample is compared to every other sample in the testing company's data base. If two people share a significant amount of DNA, like the 6.25 percent from the great-great grandparents, they are likely to be closely related.

Autosomal DNA is accurate for finding relatively recent ancestors. It gives people an advantage when doing genealogical research. The genetic links it reveals can uncover relatives that the normal methods of researching usually miss because the databases carry DNA samples from around the world.

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