We strongly recommend Family Tree DNA's Big Y-700 test as the best and most thorough, reasonably priced Y-chromosome DNA test available. The 37-marker "Y-37" test is a very economical way to begin, however. You can always upgrade later.
Since the Stephens/Stevens Project is a Y-DNA project, what we are primarily interested in are SNPs (Single Nucleotide Polymorphisms) on the Y chromosome. Currently the best test for those is Family Tree DNA's Big Y-700. The Big Y-700 will show you where you are on the Y-chromosome phylogenetic tree and which of your matches is truly closest to you. It can reveal the fine details of family branching, connect you to ancient Y-DNA test results, and may, at some point in the near future, even enable researchers to pinpoint the geographic origin of your Y-DNA haplogroup, perhaps down to the village. The "700" in the name of the test represents the added benefit of the over 700 STR (Short Tandem Repeat) markers that are also part of your test results.
Single Nucleotide Polymorphism (SNP) Testing
What is a Single Nucleotide Polymorphism?
The following definition comes from the National Institutes of Health's Genetics Home Reference web site:
Single nucleotide polymorphisms, frequently called SNPs (pronounced “snips”), are the most common type of genetic variation among people. Each SNP represents a difference in a single DNA building block, called a nucleotide. For example, a SNP may replace the nucleotide cytosine (C) with the nucleotide thymine (T) in a certain stretch of DNA.
SNPs occur normally throughout a person’s DNA. They occur once in every 300 nucleotides on average, which means there are roughly 10 million SNPs in the human genome . . .