[ronaldx]

It's not uneducated to use Occam's razor: if someone tests as not being the mother, they almost always are not the mother. This is an every day occurrence.

Chimerism is a possible explanation but vanishingly unlikely. Two identified cases, ever (i.e. none before this).

This is news because it's exceptional.

[voidlogic]

I'm not disagreeing with you in thinking the scam is more likely at first glance, but as soon as there was compelling evidence it was not a scam, the professionals involved should have shared their awareness of the obvious biological possibly.

The smoking gun in this case that there was not a scam, but something more going on is the fact that she was her kids aunt.

[ronaldx]

Apologies for editing my point above.

Chimerism is well-studied because it's biologically interesting, but most social/medical professionals are not expected to come across human chimerism in their whole career.

Chimerism not often documented in humans and the other possibilities (e.g. surrogacy scam) are hugely more probable explanations.

[Locke1689]

I think the parent's point is that, while rare in practice, well-qualified physicians should easily identify the unusual situation and propose the alternate hypothesis.

As an aside, this fact was of great annoyance to me when I was younger, as the child of two pathologists trying to watch the tv show House. If you're not familiar, it's a medical mystery show with a genius misanthrope doctor named House who diagnoses people with extremely rare diseases, almost killing them in the process.

It was a regular occurrence for one of my parents to walk through the room while I was watching the show, in the first 5 minutes, and throw out, "they obviously have x (vasculitis, chimerism, etc.)," thus ruining the rest of the episode for me. Of course, they never actually watched the show, since from their perspective it was just an incompetent medical team torturing some patient.

[tzs]

A site with a medical review by a doctor of every "House" episode: http://www.politedissent.com/house_pd.html

[ronaldx]

That your parents and the parent commenter react in this way ("it's obvious") is by design of the author of the piece and the author of House.

I can watch an episode of House and anticipate "they obviously have lupus", which makes me feel intelligent and satisfied even though I can see they are planting obvious clues from the very start which a diagnostician would be mind-numbingly stupid to ignore.

The same with the headline of this article. It's designed that way. In reality, you don't get to read the headline or watch the episode before making a clinical decision.

Regarding House: in mid-series episodes, I believe they occasionally subvert this by planting clues for the wrong thing. At least, I enjoyed being wrong in those episodes.

[seacious]

We don't really know how common chimerism, because it is expensive to test for. It requires sampling many different tissues/ parts of the body and comparing the gentic material found in each. Some kinds of chimerism are easy to detect and are believed to be relatively common. See: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.149...

[rcthompson]

What if a woman tests specifically as being the aunt instead of the mother, but also all her sisters (if any) test as aunts? Do we assume that the woman had a sister that none of her other sisters knew about, who she hid in the basement her whole life, impregnated with the woman's husband's sperm, raised the child as her own, repeated this several times, and then finally murdered the sister and hid her body?

[cmiles74]

I would disagree: it's certainly uneducated to use Occam's Razor as an excuse to be lazy, or perhaps to ruin another person's life based on one piece of evidence. The children's father vouched for her, she has witnesses to the birth of these children, etc. In fact, everything lines up with the children being hers except the DNA test results.

I would argue Occam's Razor decides against such a large conspiracy and, instead, points to problems with the test.

[josu]

>The state was still so suspicious of Fairchild that when she gave birth to another child, a court officer stood in the delivery room to witness an immediate DNA test.

If you go as far as that, why wouldn't you test mitochondrial DNA? Using Ocamm's razor myself, I will speculate that she wasn't able to get a very good lawyer.

[ronaldx]

I see no reason why a mitochondrial DNA test would be helpful - your point is that the mitochondria are maternally inherited?

1. Mitochondrial DNA is less apt than regular DNA to accurately identify motherhood since it has a low mutation rate.

2. The mitochondria would still come from the chimeric cells which still are a generation away from the mother's cells.

3. If you have have considered the possibility of chimerism, there are much simpler tests - e.g. the tests that they did do.

[josu]

AFAIK -and please do correct me if I am wrong - twins have the same mitochondrial DNA, therefore even if she is a chimera all her cells should share the same mitochondrial DNA.

And isn't testing for mitochondrial DNA fairly simple/cheap?

[ronaldx]

Mitochondrial DNA between twins is expected to be almost identical, but you and I also have extremely similar mitochondria: since it doesn't recombine and rarely mutates. So, you have to get to a much deeper level to identify the differences.

Even if it's now possible/cheap, that's a recent development.

mtDNA is good for finding your (maternal) ancestral group, less so for your immediate relatives.

[Someone]

"Chimerism is a possible explanation but vanishingly unlikely. Two identified cases, ever (i.e. none before this)."

http://en.wikipedia.org/wiki/Chimera_(genetics)#Humans gives an earlier case and references http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.149..., which states blood type chimerism occurs in 8% of twins, 21% of triplets.

So, chimerism in the broad sense isn't that rare. I have no idea whether that is different from what is described here, but I would think it isn't. Those blood cells have to come from somewhere.

Chimerism also occurs as a result of organ transplants.

[nraynaud]

there is no Occam's razor when you're doing an in depth investigation. Either they do a cursory DNA test or they try testing the father too, and then everything is in depth.

(well I come form a country where the judicial system is inquisitory, not accusatory, so maybe I'm biased in my point of view)

[khc]

"It's a rare condition called chimerism, with only 30 documented cases worldwide."

It's very rare but not THAT rare.