Recently, a Big Y-700 test has been completed for Clements B742594. This
is the fifth set of next generation sequencing (NGS) results we now have for men on the English arm of the I-Y33765 clade; the previous tests are two Big Y-500 tests (Clement 236748 & 282009) and two Big Y-700 tests (Clement 236748 & IN82043).
Before the completion of the latest analysis, genetic testing has established that the English arm divides into several lineages downstream from I-Y33767, possibly at some time during the later decades of the sixteenth century. Further, using the documented genealogies of the five men known to be derived (+) for Y33765 it seems probable this divergence happened between Clement/s male lines that were living in the valley of the River Chew, North Somerset.
As I discussed in my June blog, a comparison of 111STR results for Clements B742594 and three Clement men (236748, 282009 & IN82043) gave a hint, based on repeat values at two markers DYS481 and DYS717, that he was more closely related to Clement 236748 & Clement 282009. All three men share a 26 repeat motif at DYS481and they also have a 19 repeat motif at DYS717. In contrast, Clement IN82043 has 25 repeats at DYS481 and 20 repeats at DYS717. So, using these STR comparisons, in the June update I speculated that downstream from I-Y33767 the English branch divided, with Clement 236748 & 282009 with Clements B742594 in one group and Clement IN82043 in the other. As we will see my speculation was correct about there being a branch below I-Y33765 but entirely wrong about the way in which these four men are related.
This error became clear immediately we had the complete Clements B742594 Big Y-700 result. This shows that Mr Clements is ancestral for three SNPs for which each of the Clement men (236748, 282009 & IN82043) are derived. These mutations are BZ4354, FT314945 & FT324244 and we can now see that they divide the Chew Valley Clement/s into two distinct branches downstream of I-Y33767. Hence, because of these definitive "next generation sequencing" (NGS) data from Mr Clements Big Y test we can reject my mistaken conclusions based on STR comparisons and instead be confident of this division defined by the BZ4354 SNP. This relationship is illustrated in our new I-Y33765 chart shown below.
Rather than removing the previous blog (June, 2021) that contains my incorrect assessment based on the STR comparisons, it seems to me that, together with this update, it illustrates the pitfalls of relying solely on STR markers and once more demonstrates that only SNP mutations provide a "gold standard" genetic assay for genealogy.
Click on image to enlarge
