Re: Z17911 BigY

Jared Smith
 

To add a some additional thoughts on this...

- You can see the four SNP test result states in Alex's mutations
matrix at the Big Tree.

- How do we know Thomas and Bennett are BY11573 if their results are
'maybe'? Because it would be incredibly unlikely that it's mere chance
that they both show this particular mutation at this exact location
that also aligns with a proven SNP. FTDNA, however, is super
conservative about making such assumptions.

- While FTDNA does not report 'maybe' results for Big-Y, it does for
SNP Packs. It shows these with an asterisk and describes them as "no
calls". My SNP results show BY4028*, for example. Even though this SNP
was a 'maybe' test result, because my terminal SNP is downstream from
it, I know I have it.

- FTDNA uses some unknown formula or method to sometimes define 'solo'
terminal SNPs - when only one person has tested positive for it. For
example, Pillsbury shows terminal SNP of BY13850 even though he's the
only one to have ever tested positive for it. Hays (N28178) similarly
is alone with BY13845. On the other hand, Joel Hartley shows terminal
SNP of Z17911, even though he alone has the A11130 SNP. I'm not sure
how they determine which solo SNPs are worthy of 'terminal' status. I
generally use FTDNA's determination in marking the haplogroups of my
tree - http://dna.smithplanet.com/media/Z16357-SNP-Tree.pdf - as
verified or theoretical.

- Remember the term "terminal SNP" is a misnomer - it really means
"temporary terminal SNP" - it's the last one we can reasonably
verify... for now.

Jared

On Thu, Feb 2, 2017 at 7:25 PM, Jared Smith <jared@...> wrote:
There are really four levels of reporting for each SNP: positive,
negative, maybe, and no coverage.

The 'maybe' results (this is my terminology, not FTDNA's) are markers
where you show the SNP in your raw results, but it was in a
questionable read area of the test. This means you probably have the
SNP, but FTDNA takes a very conservative approach and does not report
these. If additional people on your branch get 'maybe' results for
that same SNP, the more likely it is a valid SNP for that haplogroup.
A positive test for that SNP verifies it as a good one and (usually)
establishes it on the tree.

No coverage means the test didn't read in this area, so you can't
really know from that test alone. If you do, however, test positive
for a downstream SNP, then you'll know you also have all upstream
SNPs, even if your test results show 'maybe' or no coverage results
for them.

My tree and FTDNA's tree has Merrick two branches downstream (BY11573
and a terminal SNP of BY11565), from you and I who are at Z17911. So
this is the 2 SNP differences.

But Thomas and Bennett also have BY11573, so this means they should
show a 1 SNP difference to you, right? The answer would be yes, except
that Merrick, Thomas, and Bennett all were 'maybe' results for
BY11573, so FTDNA doesn't count these. You'll see that Thomas and
Bennett still show terminal SNP at FTDNA of Z17911, not BY11573.

So why does Merrick get credit for BY11573 when his 'maybe' result is
the same as Thomas and Bennett? Because we know BY11573 is a valid SNP
because of Goff's positive result for it. This established its
definitive location on the tree. While Thomas and Bennett don't get
credit for it because of their 'maybe' results (they show 0 SNP
differences to you), Merrick does because his terminal SNP is
downstream from it. He can't NOT have it, even though his results were
'maybe'.

This highlights how valuable Goff's SNP pack results were to our part
of the tree. They really verified two more haplogroups - BY11573 (the
first positive result after three 'maybe' results) and BY11565 (the
second positive result with Merrick).

Hopefully that helps.

Jared


On Thu, Feb 2, 2017 at 7:16 AM, Joel Hartley <joel@...> wrote:
Does anyone know why I have a 0 SNP difference to Thomas and Bennett and a 2
SNP difference to Merrick on the Big Y?

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