Question about 1/2 second cousins #dna


Sarah L Meyer
 

Genners,
I am fairly new to DNA testing. In April I did the family finder test
and my mtDNA. After learning that my DNA confirmed that I was 100% Jewish
and that I had a large number of matches, I started testing cousins to try
to triangulate my results (so that I could figure out which matches came
from which lines). I then tested my second cousin on my father's side and
our match came out where it should. Because one of my second cousins once
removed is elderly and not in good health, I tested him next, and the
suggested relationship was "distant" cousin according to family tree DNA. I
ran the same data through GEDMATCH.com and the suggested relationship (using
their defaults) was 3.5 generations to MRCA (most recent common ancestor) -
which would be consistent with second cousin once removed. It appears that
we may only be related in one way, which means that the correction factor
for inbred populations - lost a true relationship (I think that this is what
would be called a type I error). This extra distance has not helped with
the triangulation.

In particular I am a suspected member of a Rabbinical family >from my family
finder results (until now I have had no Rabbinical ties in the 40+ years of
paper trail genealogy). My grandmother apparently told my mother that she
had "Yichus" but no one ever knew how). I am especially interested in which
line this Rabbinical family may come through, and my grandmother is my
leading candidate.

Now my paternal grandmother was the only child of a widow who married a
widower, there are descendants of her half siblings, who would be my 1/2
second cousins. Given the problems that showed up when I tested my second
cousin once removed, is it worth it to consider testing them to help
triangulate? I would be able to find one male 1/2 second cousin on her
father's side and a female 1/2 second cousin on her mother's side.

I am interested in what your thoughts are about this. I have not contacted
these cousins yet, because I don't know if it would be worthwhile.

Sarah L Meyer


Steve Adelson <sjadelson@...>
 

Hi Sarah,

First off, you may not wish to take MRCA on GEDMATCH at face value, as I
have found it not to be accurate for Jewish populations. I have a ton of
matches there, all of which list as between 3 and 4 generations, absolutely
none of which have I linked to my family via paper trail.

Regarding your situation, testing your 1/2 second cousins can help.... Any
matches with you will be through that side of the family, specifically
through whichever of your grandmother's parents was common to the
half-siblings. However, it is also possible that your great-grandparents
(the widow and the widower) were themselves related further back, so that's
something to keep in mind.

For what it's worth, you and I show up as "4th to distant" cousins in FF,
and my YDNA testing has matched me very closely to known descendants of the
Helperin rabbinic line. Those lines intermarried a lot, though, so that
doesn't really narrow it down.

Best,
Steve

-----Original Message-----
From: Sarah L Meyer [mailto:sarahlmeyer@suddenlink.net]
Sent: Sunday, January 08, 2012 2:05 PM

I am fairly new to DNA testing. In April I did the family finder test
and my mtDNA. After learning that my DNA confirmed that I was 100% Jewish
and that I had a large number of matches, I started testing cousins to try
to triangulate my results (so that I could figure out which matches came
from which lines). I then tested my second cousin on my father's side and
our match came out where it should. Because one of my second cousins once
removed is elderly and not in good health, I tested him next, and the
suggested relationship was "distant" cousin according to family tree DNA. I
ran the same data through GEDMATCH.com and the suggested relationship (using
their defaults) was 3.5 generations to MRCA (most recent common ancestor) -
which would be consistent with second cousin once removed. It appears that
we may only be related in one way, which means that the correction factor
for inbred populations - lost a true relationship (I think that this is what
would be called a type I error). This extra distance has not helped with
the triangulation.
...