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Tuesday, September 30, 2008

What is an SNP and what is M172?

For many of us who have tested our Y Chromosome for genealogical purposes or to discover our paternal ancestral origins, these are questions that might be considered basic and possibly even uninteresting. But since this is our first blog post, we might as well start with the basics so everyone can be brought up to speed.

SNP stands for a Single Nucleotide Polymorphism and it refers to a DNA sequence variation that occurs in a single Nucleotide (A C T or G) in the genome sequence. When one of these changes in some way, we call this a Single Nuleotide Polymorphism or SNP for short. These SNP's, when found on the Y Chromosome, can be used as markers of descent on the paternal tree of life, thus acting as a way of determining relatedness among different people.

So, what is M172? In short, it would be the 172nd Y chromosome SNP discovered by scientists. It is also referred to as Haplogroup J2 and is a genetic marker carried by men originating from a region ranging from India to Spain. All men carrying this genetic marker share a common paternal line ancestor. Haplogroup J2 or M172 is especially frequent in men from the Near East and the eastern Mediterranean. This blog will try to unravel the story of M172 and his descendents, discussing specific branches of Haplogroup J2 and the peoples who spread this marker from the Neolithic right through Roman times.