The NA ules

as of 1-17-13

This explains a lot about the DNA test, mutations and gives a good view of what they mean. It was done by Bennett Greenspan, the president of Family Tree DNA who was good enough to supply most of this information with an understanding that many projections and opinions may change in the future as the science matures. Bennett has been very helpful to let us have this explanation.

The results from a search of the Haplogroup database not only provides information about your deep ancestral history, but the outcome can also be used to analyze Y Chromosome results.  Since the Haplogroups are the branches, and the Haplotypes are the leaves of the tree, if any of the McTernans belong to different branches, no matter how close their Y DNA test results were, the individuals are not related.  

All of the McTernan DNA Groups, Craig Dowd, the Tiernans and Philip O'Rorke fall into the larger DNA group called the Haplogroup R1b which is the most common haplogroup in European populations. It is believed to have expanded throughout Europe as humans re-colonized after the last glacial maximum 10-12 thousand years ago. This lineage is also the haplogroup containing the Atlantic modal haplotype.

If you match another McTernan 25 / 25 you have a 50 % probability of a common ancestor within 7 generations or about 175 years. A 90 % probability that the common ancestor is within 20 generations (500 years) and a 95 % probability that the common ancestor is within 30.4 generations or 760 years. While these may seem like long odds, Leo and Eoghan turned out to be 4th cousins with their Great Great Grandfathers being siblings. A well done web site on how to estimate the time to the most recent ancestor is at http://nitro.biosci.arizona.edu/ftdna/TMRCA.html

The individual digit (known as an allele) by itself  does not matter, what counts is if the allele in each column matches the ones above or below it. Then how many markers or alleles match, exactly, out of 25.

The rules for matches in general: these are numbers so how they are interpreted is key. They are good indicators. The 25 loci test is very new so there is very little experience to state exactly where the cut off point is. With that said, most likely a 23 / 25 or better match means you are genetically related. Less than a 23 / 25 match most likely means no common genetic ancestor or beyond 2000 years back in time, certainly before our surname arose.  Surnames began c. 1120.

DYS 464 (the last 4 markers shown) are a dynamic set of markers. Due to the way that DYS464 is sorted most mutations in the 4 DYS' 464a, b, c and d might be counted as one, perhaps two mutational events, and a special algorithm was just put in place at FTDNA to handle this marker. The University of Arizona and Family Tree DNA have set up a special scoring system that sometimes affects this marker.

The German study: As an example of the haplogroup situation, Ron German is a 21 / 21 match with Jim McTiernan (CA) and a 20 / 21 match with Mark and Michael (CN) and a 19 / 21 match with Scott, Tom and myself and a 18 / 21 match with John (USA). Ron is researching his family and believes their origin is in Wales at this point in time. Way back in time our families may be connected or this is a great example of the haplogroup effect. The format and layout of this page, along with some very helpful formatting points is by courtesy of John German who is also the administrator of that family's DNA study at http://www.inct.net/~german/dna.htm Tony Mitchell is a 24 / 25 match with Jim (CA).

Note: DYS 389ii would include any mutations that might have occurred in both 389i and 389ii. For some reason that is how all the major DNA labs report them. While this could be confusing it appears not to have any impact on our DYS scores. In general, it appears that Loci 4, 8 and 21 mutate with a higher frequency and also in general, loci 21 seems to have more 2 step mutations than the other loci.

Male DNA testing looks at various locations on the Y chromosome. At a locus, there might be 10 to 30 alleles, or identification markers that seem to be highly valuable for Anthropology or genealogy study. Please also understand that locus changes (mutations) can occur at any time . . . and always between a father and a son. Using the Y chromosome mutation rate PER MARKER of once every 500 generations, if 15 loci are measured, 500 divided by 15 = every 30 generations there most probably will be a mutation occurring between 2 males of the same lineage. If 17 loci are measured, 500 divided by 17 = every 29 generations. At 21 loci being measured, 500 divided by 21 = every 23.8 generations, 500 divided by 25 = every 20 generations or 500 years there could be a mutation at a locus. This is an average as the mutation could and does occur at any time . . . i.e. randomly.

Now here comes the part that can hurt your head unless you are a mathematician. All of our DNA scores are based in good hard science and are true and real for every locus. The question that now is asked, what do they mean? The scientist now take a back seat with the statisticians taking over to give their numerical based opinions. Worse, each locus may well have a different rate of mutation, some faster and some slower. Because the scientists don't have hard mutation rates we are currently following their suggestion of 1 mutation "event" per 500 generations per locus (marker). Likewise, loci 464a, b, c and d have a peculiarity about them that appears to mean that 2 or 3 mutations among those 4 loci should be counted as only one, or perhaps 2 mutation. This would mean that Scott (AU)'s score would be 23 / 25 rather than 22 / 25 off the T Group baseline.  Scott genetic distance score is 22 / 25. 

At this point in time most DNA experts think a generation is 25 years on average. When I run the math on my whole family line for all 8 families, the average generation span is 29.6 years. For our DNA test purpose I have used the geneticist version of 25 years. The Y chromosome mutates on average once every 500 generations or 12,500 years PER MARKER in each locus. The trouble is you don't know when.

The townlands of origin, group matches, individual ancestor lines and family origins  for the DNA testers are at http://mctiernan.com/dnatest.htm 

The McTernan very graphical Phylogenetic Tree Chart that shows genetic distance and skew is at http://mctiernan.com/mctiernangrid.htm

The genetic and geographic maps of all identified MacTighernan families are at http://mctiernan.com/McTmaps.htm

Click here to send E-mail michael@mctiernan.com