Saturday, April 14, 2012
Tying a Y-DNA Mutation to a Specific Ancestor
A while back, I posted regarding the three families who bear my surname and the possibility of doing Y-DNA testing to prove if all three have a common ancestor. Back last fall, we were able to confirm that yes all three Owston groups had a common source.
Three of the participants – one from each family – even matched at 100% indicating the modal haplotype for the surname. We have since continued the study and are attempting to test at least one person from all 23 extant lines of Owstons and Oustons. Currently we have 17 participants – with results presently returned for twelve. Since three lines have two participants, 14 out of the 23 Owston lines (61%) are represented. Eleven distinct lineages (48%) have returned data.
Today we received the latest results in the Owston/Ouston Y-DNA project and I am pleased to announce we are able to determine where a Y-DNA mutation entered a specific family grouping – the Thorpe Bassett branch of the Sherburn Owston family.
Because we have so few lineages in which to test, I had no indication I would be able to narrow down a specific mutation to a particular generation or person; however, today, we can isolate the source of a mutation on the DYS442 marker. Typically in our family, this marker has 17 repeats (FTDNA counts 12) of the code TACT; however, we have two individuals from the Thorpe Bassett branch of the Sherburn family that have a loss of a repeat with a series of only 16 (FTDNA counts 11) on DYS442.
Y-DNA mutations are harmless as they do not affect the genetic makeup of a person nor do they have any adverse effects on someone’s health. These are changes that occur in the number of repeats of a sequence in a non-coding region (sometimes called “junk DNA”) on the Y chromosome. These single tandem repeats or STRs are slow to mutate and, therefore, provide the ability to conclude whether someone is from a particular lineage or family.
The first person to display this mutation, as well as another a two-step mutation on DYS458, was our subject identified as Sherburn03 of the Durham line. Without the ability to triangulate when these mutations occurred, the best we could hope for is to identify both mutations as occurring with or downstream from Peter Owston who was born in 1661.
Since Peter’s brother John’s descendent from the Richard Ouston lineage did not have either one of these mutations, we knew that the DYS442 and DYS458 mutations were not upstream from these brothers, but could not determine where in Sherburn03’s lineage either of these occurred. That was until today.
While his descendents have lived in England, Canada, Australia, and the United States; only three extant lines descend from Peter Owston (1661-1699): the Lincolnshire line, the Durham line, and the Michigan line. We are currently awaiting results from one of the two living male members of the Michigan line. Sherburn06 is the last living male in the Lincolnshire line. Only the Durham line has multiple Owston males that constitute three generations of that particular lineage. Several other lines descended from Peter Owston became extinct during the twentieth century.
Since the DYS442 mutation is the only one occurring in Sherburn06’s results, it is currently impossible to determine at what point Sherburn03’s other mutation of 16 to 18 on DYS458 had occurred. Because the Durham line is the only extant line from John Owston (1696-1770), it will never be possible to determine where this other mutation occurred as there are no other relatives through which to triangulate the results. It could be anywhere within a range of seven generations that includes both Thomas Owston (1696-1770) and the subject himself.
Since Sherburn06 is only one marker different from the modal haplotype, his Y-DNA is 97.67% similar to the unknown common ancestor of all Owstons – an individual who probably lived in the mid to late 15th century.
While I never imagined being able to determine when a mutation entered the Owston family, this provides hope to be able to identify the source of additional mutations found in other lines through additional testing.
For the latest version of the study, see http://www.owston.com/dna/Owston_Family_Y-DNA_Study.pdf