We have learned that the term "haplotype" refers to a set of Y-chromosome STR marker values. For instance, 11 14 12 13 29 24 10 13 13 14 12 15 12 12 13 12 12 12 14 25 19 30 is a haplotype.

We have also learned that a mutation can occur at any STR marker location. For instance, a change from 30 to 31 in the above haplotype would be a mutation.

There is another type of DNA mutation which is called a Single Nucleotide Polymorphism (SNP). A SNP is a change in a single base pair on the DNA molecule.

SNPs on the Y-chromosome are very rare, but when they occur, they are passed down unchanged from father to son for literally hundreds of generations. SNPs can, in fact, be used to define entire populations of men.

Populations that have the same Y-SNPs are said to belong to the same haplogroup. Y-chromosome haplogroups are listed by letter - Haplogroup J or Haplogroup Q, for instance.

Most haplogroups can be subdivided into smaller groups. For example, Haplogroup R can be further divided into "R1a" and "R1b".

Haplogroups are useful for population studies, but have somewhat limited application in genealogy. Since SMGF is focused primarily on the application of DNA testing to traditional genealogy, SMGF does not display haplogroups along with haplotypes.