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Irish Type III

From ISOGG Wiki

The Irish Type III project is a Y-DNA geographical project hosted at Family Tree DNA.


In February 2006, In response to a question on the [email protected] email list, Dr Ken Nordtvedt identified a small R1b cluster that he had found was centred on the counties of Clare, Limerick and Tipperary in Ireland.

The definitive markers Ken identified for this cluster are:-

  • DYS 439 = 11
  • DYS 456 = 15
  • DYS 459 = 8,9
  • DYS 464 = 13,13,15,17
  • DYS 463 = 25

As two other Irish clusters had been identified as "North West Irish" (Irish Type I) and "South Irish" (Irish Type II), this cluster was called "Irish Type III" and the name has stuck.

Y-search ID NT4BZ has been set up for the Irish Type III cluster modal values.


When haplotypes with these definitive markers were studied, it was found that that the surnames, O'Brien/Bryant, Hogan, Kennedy, Casey McGraw/McGrath and Crow(e) are seen frequently. It has been shown that Irish Type III is the STR signature of the Dál gCais or Dalcassians, the descendants of Cas b347CE.

A paper has been written in the Journal of Genetic Genealogy setting out this research. The paper is entitled "A Set of Distinctive Markers Defines a Y-STR Signature for Gaelic Dalcassian Families".


Age of cluster

Using geneticist Anatole Klyosov's methods, a calculation using 336 haplotypes of 67 markers conducted in September 2014 gives a figure of 1450 ± 150 years to the most recent common ancestor (MRCA). The MRCA for this cluster lived between 350 AD and 650 AD.

Defining SNP

The cluster was shown to be L21+ when this single-nucleotide polymorphism (SNP) was discovered and for some time Irish Type III was just another L21 cluster among several.

Using Family Tree DNA's Walk Through the Y project, a defining SNP was discovered for this cluster in November 2009, which is called L226. ALL Irish Type III who have tested this SNP have recorded a positive result. Haplotypes for all other clusters are recording negative results for L226.

SNP L226 is recognised by ISOGG on their yDNA Haplogroup R Tree as R1b1a2a1a2c1f2a.

A project has been established at FTDNA for those testing L226+.

With the availability of NGS (Next Generation Sequencing), several branches have been established below the L226 SNP. These are shown on the R-L226 Project, see Link below.