
First reported case of a paternity test fooled by a human “chimera” - xivzgrev
http://www.buzzfeed.com/danvergano/failed-paternity-test-vanished-twin
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ghshephard
What I find particularly interesting, is that the "accredited lab" (presumably
accredited by the FDA), just came back with a (misleading) negative result,
but that 23andMe, which presumably was not accredited by the FDA at the time,
provided results that cleared the issue up.

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pcrh
Finding that the father has contributed ~1/4 of his genes to the child would
normally exclude them from being described as the biological parent, who would
normally contribute ~1/2 his genes to the child.

Possibly the father had no brothers, therefore no-one else could contribute
even 1/4 of the genes (unless the child is a chimera from two fathers...).

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Udik
Well, they are _his_ genes. Just not for the whole body.

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pascalmemories
Rather suspicious, repeated, mentions of 23andMe. This reads more like an
advertisement in disguise rather than "news".

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cma
Yep, they are doing a big PR push after the FDA approval. Many articles that
were in the can released at once.

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Asbostos
It's a bit scary that this was detected when the parents used a fertility
clinic and were so sure of themselves that they felt the need to investigate
further. There must be other false negatives where they trusted the test
results that perhaps led to relationship breakups or other problems.

~~~
kbutler
Yes - every other case where paternity tests have failed has simply been
unreported, or not investigated sufficiently to invalidate the test.

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Jabbles
Why do the standard paternity tests not notice when someone is effectively the
child's uncle? The genes must match to a far greater extent than an
"unrelated" person. Is that information lost between the actual test and the
"yes/no/probability" result?

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jfoutz
Brothers and sisters only share 1/4th dna. brother A gets 50% of dad's genes.
Brother B also gets 50%, but not (necessarily) the same 50%. same process on
the mothers side.

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Udik
So it's 1/2 shared dna for siblings, not 1/4th. Only (I think, possibly) it's
1/2 on average instead of being _exactly_ 1/2 as in the case of parents and
children.

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jfoutz
Ah, I did the table wrong in my head. You're right. 2 genes, one from father
one from mother, sibling A along the top, simbling A down the side.

    
    
           MM MF FM FF
        MM  1 .5 .5  0
        MF .5  1  0 .5
        FM .5  0  1 .5
        FF  0 .5 .5  1
    

(4+ .5 * 8 + 0)/16 = 8/16 = 1/2

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djyaz1200
Seems like this is a big deal for criminal justice system.

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spacemanmatt
They'll ignore it like they ignore most of science.

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xivzgrev
"How can a man who was never born father a son? When the ghost of his genes
lives on in the DNA of his brother, genetics researchers have found. A
34-year-old U.S. man is the first ever reported case of a paternity test
fooled by a human “chimera” — someone with extra genes absorbed from a nascent
twin lost in early pregnancy."

Thought this was super interesting and thought I'd share!

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jonah
...and how we're unique individuals from the very very beginning. Pretty
wonderful/amazing.

~~~
reddytowns
We're about as unique as combination locks are unique from each other.

Sure, we, mostly, each contain a unique set of chromosomes, but there are
copies each of our chromosomes spread across the population of the world. So,
losing one unique set, isn't a big deal at all. In any case, the next
generation will again just be a random set, and your influence on that in
aggregate will be most likely minuscule.

~~~
pbhjpbhj
That analogy is like "a piece of fecal matter on the bottom of your sneaker",
they're both written with letters.

People are not just DNA, identical twins are not even identical. We are all
demonstrably unique.

~~~
kbutler
You're unique...just like everybody else.

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Tiquor
This is far from the first case. There was a case related to welfare benefits
that ended up with a woman fighting for years to have people believe her baby
was hers.

~~~
edmccard
That case involved a maternity test, not a paternity test.

It's even mentioned in the article: "A similar case in 2006 saw a 26-year-old
chimeric woman, Lydia Fairchild, almost lose her children after maternity
tests required for welfare payments suggested she wasn’t actually their
mother."

~~~
Udik
What's the difference between a paternity test and a maternity test? Will
there be a "first case of paternity test fooled by chimerism" for an asian/ a
person under 22/ a person with blonde hair?

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DanBC
A maternity test tells you who the genetic mother is. A paternity test tells
you who the genetic father is.

The legal system sees genetic forensic evidence as very strong. This result
shows that we need to be a bit more careful about the samples we used for
genetic testing - although this means police procedures for extracting samples
are going to get a lot more complicated than a simple cheek swab.

~~~
Udik
> A maternity test tells you who the genetic mother is. A paternity test tells
> you who the genetic father is.

Which is, from the point of view of the test, exactly the same thing. However,
it's obvious that "mater semper certa est" ("the mother is always certain").
That is, almost always, apparently...

