Sally:

As I am sure you know, each cell has many mitochondria and each
mitochondron has many copies of the DNA molecule. In a mtDNA test, a
heteroplasmy is called at a particular position on the mtDNA sequence
when it is found that some of these molecules have one value and some
have another. If a heterosplasmy is detected the laboratory can report
it as Ancestry.com apparently did on your first test, or they can just
report the dominant value. I do have a lot of respect for the accuracy
of Family Tree DNA, but unfortunately they apparently take the latter
approach and do not report hetroplsamies as such. Ancestry.com
apparently detected the heteroplasmy in your initial test and reported it.

But why didn't your younger brother's report show a heteroplasmy? It is
difficult to detect low levels of a heteroplasmy. For example, if 90%
of the molecules are of not value and 10% are of the other, the
heteroplasmy may have gone undetected. I suspect Ancestry.com simply
did not detect it in your brother's test.

But why weren't you and your brothers values the same? One way of
looking at a heteroplasmy is to consider it as a mutation in
transition. It can complete the transition or revert to its original
values. When cells divide, the mitochondria do not divide evenly and
subsequence cells can migrate in either direction. Even though you and
your brother have the same mother, she most certainly did not pass
exactly the same proportion of the heteroplasmy to each of you. There
is randomness both in the process of passing on the mitochondria and
well as randomness of what happens to heteroplasmy as the fetus grows
into adulthood. The heteroplasmy in your brother was apparently a T and
yours was a C.

By the way, a polymorphism at position 16090 is apparently very rare.
It does not occur in my reference database, nor was it reported in last
yearss report from the Genographic project. I think you just happen to
catch one of those "private" events.

====================
J. J. (Jim) Logan
Group Administrator, J-mtDNA and Logan DNA Project
Owner/Moderator, J-mtDNA and GenGen-NV Discussion Groups on Yahoo
===================================================================



kinbuch wrote:
>
>
> Previously, my Ancestry.com mtDNA testing revealed a heteroplasmic
> situation at 16090 in the HVR1 region and they typed me as 16090Y and
> in the haplogroup J.
>
> My younger brother's Ancestry.com mtDNA testing did not reveal the
> heteroplasmy and he was typed as 16090T and also in the Haplogroup J.
>
> I just received my Full mtDNA results from FamilytreeDNA.com and they
> typed me as 16090C and in the haplogroup J1c.
>
> I understand from previous posts that the FamilyTreeDNA testing is the
> more accurate, but I find it quite disturbing to have such a variance
> in the 16090 call. And yes, we have the same mother.
>
> Any insights, or should my brother have his mtDNA tested with
> FamilyTreeDNA?
>
> Sally
>
>