So far we have identified 15 distinct genetic groups, and also subgroups within some groups. You can view the results on the Family Tree DNA website.
To give you an idea of the differences among the various groups, here are the recent ancestral connections of the first two Bryson Groups. When particpants are tested they are asked to identify their known country of origin. So after you are tested you see how many people in the data base you match (by country.)
The largest group, B1, is connected to the Bryson City, North Carolina line of Bryson. In this case, some members might claim Northern Ireland (but suspect Scotland), others may go ahead and claim Scotland. Five people from this line have been tested, so four matches are simply other Brysons.
Here is the result for the B1 Brysons, notice they have very few connections in the data base.
Now compare the above results with the Bryson group B2 connected to John Bryson, b. 1690 in Northern Ireland (not genetically related to B1.)