Genetically speaking, my sisters and I are all half Mom and half Dad, right? DNA 101. So, only one of us needs to do a DNA test, and then we’ll all know our ethnic origins, correct? . . . OK, I confess I never took DNA 101. But thanks to AncestryDNA, I have learned the answer is no (at least when it comes to autosomal DNA). The more family members you test, the fuller the picture of your genetic genealogy will become.