Thank you for your interst in the Yarbrough DNA Project.We have learned since that posting that according to the Yarbrough Archivists of the National Yarbrough Genealogical and Historical Association, Old Richard is proven by his will to have had two sons, John and Richard Jr., but their children are unknown. There is about a two generation gap in proving the any connection to the lineages of Yarb(o)rough's born in the 1600's.
You are correct that the DNA test is for the paternal (male) only who carry the Y-chromosone which is unchanged voer centuries. Females test their mtDNA but is is daughter from her mother, and her mother's mother on back.
We would welcome any male descendant from your line to participate.
Look over the project and please have a male relative join.