Re: Z17911 BigY

Jared Smith
 

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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