Chimeras walk among us...

September 24, 2003 12:35 PM

“Hybrid Humans” Very early on in the womb, two fertilized eggs that would have normally created fraternal twins will occasionally fuse to form one embryo, producing a "chimera": one person with two sets of DNA. The link goes to a Nature article, here is an NPR piece.
posted by o2b (14 comments total)

I head that story the other day just as I was waking up - in that groggy space between consciousness and sleep. It really freaked me out.
posted by aladfar at 12:39 PM on September 24, 2003

Hypothetical: A chimera is arrested, with motive, opportunity and no alibi. A hair is found at the scene of the crime. Its DNA is tested against the DNA of the suspect -- not the same!

It's a Law and Order situation -- imagine the appeals that would hit the system if DNA evidence were found to be unreliable.
posted by o2b at 12:51 PM on September 24, 2003

02b--that's exactly the kind of scenario mentioned in the NPR piece, which is fascinating in general (everyone should give it a listen). The reporter makes the point that if you, say, collect hair from the crime scene, you need to collect hair from the suspects to establish the DNA--a cheek swab might be DNA from your "missing twin". Or your hair might be. Uhh, whatever--it's hard to keep straight.

Also interesting is that chimerism is thought to be "very rare" but nobody knows how common it really is.
posted by adamrice at 1:16 PM on September 24, 2003

awesome. I hope I'm a chimera, coolest thing I've heard about in a while, thanks for link.
posted by dabitch at 1:46 PM on September 24, 2003

(eh, but i'm not a hermaphrodite... just to clear that up. heh.)
posted by dabitch at 1:48 PM on September 24, 2003

Fascinating article. Good post. Perhaps chimerism/mosiacism is more common than we now think-- it used to be thought that having twins by two different fathers was extremely rare. Now that we have DNA typing, it's been found that it is much more common than previously thought (but still somewhat rare.)
posted by Shoeburyness at 2:53 PM on September 24, 2003

Sometimes I wish I was a mozilla.
posted by shoepal at 2:58 PM on September 24, 2003

Although it is not unknown for an egg to start developing without being fertilized, fully parthenogenetic human embryos cannot develop to term.

With one possible counter-example having been reported in the Bethlehem region, approximately 2007 years ago.
posted by yhbc at 3:01 PM on September 24, 2003

Any "overlords" comments and I swear I'll jump through your monitor and punch you in the neck. You've been warned.
posted by Samsonov14 at 3:05 PM on September 24, 2003

I, for one, welcome our new running-gag overuse guardian.
posted by adamrice at 3:36 PM on September 24, 2003

Damn straight.
posted by Samsonov14 at 5:05 PM on September 24, 2003

Fatherless children have a hard time when father is God, lord.
(with deep, deep apologies to Blind Willie Johnson and the Rev. Gary Davis)

It's a Law and Order situation -- imagine the appeals that would hit the system if DNA evidence were found to be unreliable.

Not necessarily... This doesn't mean identical DNA samples can be from different people, but rather that non-identical DNA samples can be from one person. (As I understand it--I'm no molecular biologist.) So it probably wouldn't be useful to overturn DNA evidence convictions, but might make it harder to use DNA to prove people's innocence.
posted by arto at 1:05 AM on September 25, 2003

"I'm convinced that on the streets of London and Hamburg there are many undetected chimaeras," says Rudolf Happle, a dermatologist at the University of Marburg, Germany

Fascinating post, o2b.
posted by hattifattener at 1:35 AM on September 25, 2003

With one possible counter-example having been reported in the Bethlehem region, approximately 2007 years ago.

And one other possible counter-example a long-long time ago, in a galaxy far-far away...
posted by joquarky at 1:51 PM on September 25, 2003