Michael Cooley's Genetic Genealogy Blog GEN • GEN
23 August 2016

Big Y Ordered for Cooley Group CF04

FTDNA kit #342788, a Davis, is a Y-STR match to the CF04 Cooleys. He's had 10 million mutations tested on his Y chromosome (the Big Y) resulting in a terminal SNP now known as YP4944. Additional mutations were discovered that had emerged in his lineage since YP4944 but, so far, only he is known to have them. That's about to change.

Kit #76628, a descendant of Robert Cooley (1754-1794), has just submitted his sample for a Big Y. The results will not tell us precisely how the Cooleys are related to the Davises but, as with the Davis tester, will provide a general timeframe and a discovery of all the previously unknown mutations that came into the CF04 lineage since the Davis/Cooley mutual ancestor. Although the measuring tools are different, this works much the same way astronomers determine the distance between earth and the stars: triangulation. The first graphic illustrates the method.

Mutations found in Y-STRs, those displayed in the Cooley DNA Project, are largely unreliable. They're fickle and tend to occur relatively quickly throughout a lineage and can even revert back to earlier values. Occasionally, an STR does prove itself to be relatively consistent over a large number of generations. A couple of them are found in the CF01 group. However, this appears not to be the case for CF04. I've tried, but have been unable to determine any pattern. Most of the mutations—or mismatches—in CF04 appear to be truly random. That's why the count of mismatches, also known as the genetic difference, is more useful in providing an estimate of STR relatedness between testers, not the mutations themselves.

SNPs (Single Nucleotide Polymorphisms) are different. Unlike the repeated strings of bases, or STRs, a SNP mutation happens to a single base. Its nucleic value, one of four molecules, mutates to another. Geneticists will shorthand such a change in the manner of A → T. The Davis terminal SNP, YP4944, which occurs at position 8012374 on the Y chromosome, is G → A and may be as much as 1500 years old. In other words, the most recent common ancestor (MRCA) the Davis tester has with those now represented in the SNP database lived in about 500 AD! In fact, the tester's earliest known ancestor (EKA) is William Davis who died in Abbeville, South Carolina in 1825. Although we have no idea when the Davis / Cooley MRCA lived, the test results will provide a significant clue. I feel confident the MRCA of the Davis and the CF04 Cooley lineages will be considerably more recent than currently and that the results will initially produce at least one new haplogroup under YP4944.

With this new test, we'll learn something about the degree of relationship between the Cooleys and the Davises. But what of the Cooleys themselves? A second Big Y for Robert Cooley's son, Daniel, will find the SNPs the two Robert lines have in common, all the SNPs Robert was born with. (Triangulation, as shown above, will tell us that.) With that, we'll have a baseline against which to evaluate the relationships among the other CF04 Cooleys. But more on that after the new results come in.

This is what will happen in the coming weeks: FTDNA will issue a report indicating with whom the test results match and list the (unnamed) matching SNPs. Other than that, there will be no additional analysis for some time. But I'll be able to take those results and make a preliminary analysis. I'll then send information about the new SNPs to yseq.net to have them named and evaluated for reliability. (FTDNA will also do that, but it takes the company months to accomplish the task. Yseq generally finishes their job within a couple of weeks.) A highly detailed file that includes all the raw data, called a BAM file, will be requested from FTDNA. That typically takes a couple of weeks. Once ready, it will be uploaded to YFull.com. After about 4-8 weeks, YFull will have completed their own analysis of the data, generated a report listing nearly 500 new STRs, compared the results with their own database entries, and placed the tester's ID on their SNP tree at http://yfull.com/tree.

The Robert Cooley Big Y results are presently slated to be ready mid to late October, about two months away. I'll have the new SNPs sent off to yseq and my preliminary report written within about a week after that. Then once FTDNA and YFull have finished their analyzes, I'll go over them and make any needed revisions.

As always, I'm happy to answer any questions.