Last spring, Marketplace host Charlsie Agro and her identical twin sister, Carly, bought DNA ancestry kits from five of the most popular companies in the industry. Find out why some of the results they received left a team of computational biologists at Yale University baffled.
I would expect some reasonable variation between companies, but far, far less within a particular company. In all though, the article does a good job of explaining some of the basics of what is going on here.