We had John’s, a Great Grandson of Hugh, DNA tested by Family Tree DNA. We had his Y-DNA tested for 111 markers. From this we found that his DNA matched to a subclade called M222. Below are some quotes about DNA and testing that helps to understand what it all means. At the bottom of this page I put some links to sites that help to explain M222.

Quotes From Family Tree DNA Website

Y-DNA testing can confirm your genealogical connections on your direct paternal lineage and expand your understanding of your deepest paternal ancestral origins. Because your Y-DNA has been passed on to you generation after generation by your direct paternal ancestors, it offers the most exact information possible for this line.

What is a Y-chromosome DNA (Y-DNA) STR test? What will I learn?
When testing the Y-chromosome, there are two types of tests, short tandem repeat (STR) and single nucleotide polymorphism (SNP). STR tests are best for recent ancestry while SNP tests tell about more ancient ancestry. Our standard Y-DNA panels use STRs and are useful in verifying common ancestry between two males and finding genetic cousins on the paternal line.

What is a Y-chromosome DNA (Y-DNA) haplogroup?
Y-chromosome DNA (Y-DNA) haplogroups are the major branches on the human paternal family tree. Each haplogroup has many subbranches. These are subclades.

About My Haplogroup
The R-M222 lineage began in Western Europe. It is the descendant of the major R-M343 lineage. The R-M222 line spread to the British Isles. It is over 12 percent of the population in Ireland. This may be due to its connection to the Uí Néill and Connachta dynasties.

Links
M222 (formerly R1b1c7) Project
Family Tree DNA R-M222 Haplogroup Project
Testing Candidates for M222 SNPs

This Haplogroup Chart that is maintained the administrator of the R1b-L21 Yahoo Newsgroup