I took part in the Johnson/Johnston/Johnstone Y-DNA testing some years ago. There were no exact matches to mine, but some that were "close". This has so far not given any new connections, but has supplied the information that my Johnston ancestor likely came from the Aberdeen region of Scotland since all those with similar DNA that had been able to trace their lines back to Scotland were from that area. At present my "brickwall" is my Johnston who married in 1720 in Virginia but was a "William" among several others at the same time and location and I have not been able to discover his line back to Scotland..... but as more people take part in the DNA testing... I have hope maybe it will someday help make that connection.