DNA & GENEALOGY.  The first  and perhaps best place to look for on-line answers is Family Tree DNA, the Houston, Texas, based company that runs the DNA analysis for the Smothers Project (and many other surname projects):

Family Tree DNA Web Site

They are very excited about their technology, and I have found that they respond promptly to questions......their email address and telephone number are in the footer of their home page.
 

The next place to check out is Kevin Duerinck's web site, which has many helpful pages, including this discussion:

Genetics & Genealogy: Y Polymorphism and mtDNA Analyses
 

DNA 101: Y-Chromosome Testing (Blair DNA Project Web Site)
 
 

Also, a thorough discussion of  DNA analysis results from a large, older surname project (Mumma) can be found at:

Mumma Surname DNA Project Web Site
 
 
 

COMPARING INDIVIDUALS:  Genetic Distance Analysis  &  Time to Most Recent Common Ancestor (MRCA). This topic perhaps is the one that genealogists care most about.  It is not terribly difficult to understand, once you get past all the technical jargon.  Web pages with some useful discussion and links:

Introduction to Genetic Genealogy  by Alan Savin

Using Genetic Marker Similarity Between Two Individuals (Family Tree DNA )

Genetics & Genealogy: Y Polymorphism and mtDNA Analyses by Kevin Duerinck
 
 

GENETIC GENEALOGY SERVICE LABORATORIES.  Here are some links that list and compare various genetic laboratories that specialize in genealogy projects (as opposed to laboratories for such applications as forensics and medicine):

Ron Lindsay's Comparison of Lab Offerings

Kevin Duerinck's List of Genetic Genealogy Labs