Single Nucleotide Polymorphisms (SNPs)In addition to the standard STR Y chromosome kits discussed here, there are now a number of kits available for testing Single Nucleotide Polymorphisms (SNPs) on a male's Y chromosome. SNPs mutate even more slowly than STRs. Specific SNP mutation values have been used in population genetics to identify the large evolutionary branches of the Y chromosome tree within and out of Africa. For a long time the technology for extracting the slower-mutating SNP information limited its use to identifying these deep, patrilineal, ancestral branches, or haplogroups. A male's SNP-determined haplogroup, identified only in very general terms when purchasing a 12-marker STR DNA kit, held limited interest. The most recent common ancestor (MCRA) with other males who share one's deep, ancestral haplogroup lived before surnames were taken, so haplogroup matches can include numerous other surnames having little meaning to most genealogists. This is why one often sees matches to other surnames between 12 and 37, and sometimes 67, markers. Fast forward about ten years, the Y chromosome haplogroup tree determined by SNP mutations has grown considerably. Meanwhile, new, larger SNP DNA tests are being offered by companies at lower and lower cost. They are now capable of identifying many thousands of SNP mutations on one's Y chromosome. As more males order these tests, more SNP mutations that further refine haplogroup sub-branching are being discovered. As a result, we are seeing an explosion of SNP discovery. At the 2013 FTDNA project administrators' conference, Dr. Michael Hammer displayed a scroll illustrating the growth in new SNPs discovered downstream (more recent mutations) of R-M269, western europe's dominant haplogroup branch. In 2010 they had fit on one page:  Photo courtesy of Jennifer Zinck Click to Enlarge In fact SNP discovery in various haplogroups is just beginning to enter historic time and tag recorded population groups. This also means it's approaching a genealogical timeframe. Our Irish Ely Carroll subgroup is an example, where the DF21 SNP, specific STR values and documentary trails combine to describe the Y chromosome genetics of this interesting, historic cluster of Irish "clans". Additionally, using the new advanced SNP kits available, we are on the cusp of using SNPs to identify family groups within surname groups within a genealogical timeframe. So, for example, in the Ely Carroll DNA project we will begin to see not just that specific historically-related surnames match using STRs, but also what the branching structure among them is based on their shared and differing SNPs. Similar discoveries are being made in other surname and haplogroup arenas. Incidentally, the most current Y haplogroup tree is maintained not by professional population geneticists, although they are very involved in SNP discovery, but by unbelievably hard working volunteers with the International Society of Genetic Genealogy and others, many of whom have science backgrounds. You can see the ISOGG's ever-evolving masterpiece here. |
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