First reported case of a paternity test fooled by a human “chimera” | Hacker News Reader

First reported case of a paternity test fooled by a human “chimera”

buzzfeed.com

65 pointsxivzgrev30 comments

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.

It's an issue of the question they were (perhaps implicitly) asked, not competence. For example:

http://www.dnacenter.com/dna-testing/paternal-lineage.html

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...).

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

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

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

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.

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

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?

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.

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.

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

They share ½. Half-siblings share ¼ dna, because of exactly what you said. Full siblings share half of the half they got from their father, plus half of the half they got from their mother, for a total of ½.

An uncle and nephew, as in the article, would share ¼.

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

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

"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!

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

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.

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.

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

The question is, could this technically be considered polygyny under certain stretched definitions?

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.

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."

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?

Women tend to have reliable first-hand information as to whether they gave birth to a particular child, so maternity tests occur in different social and legal contexts and have different consequences. (Admittedly giving birth to a given child is not the same as being its genetic mother, but in most cases the distinction is not at issue.)

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.

> 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...

"paternity" == father

For a mother, it's called "maternity"

Many people who are learning English (as I presume you are) learn the language is genderless, but that's not strictly true.

http://dictionary.reference.com/browse/paternity

No, I'm not learning English. The test is functionally identical. The relation to chimerism is not unique for a father vs a mother. It's just came across as a silly headline to me. I read most of the article and didn't see the reference to the maternity case.

Did you read the article? Pretty sure it mentions this case.

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