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Science

Chimera Twins Story 483

skelley writes "Below is an audio link on this morning's story on NPR about Chimera twins, or people with two sets of DNA. It turns out that every once in a while a set of fraternal twin eggs merge into one embryo. The resulting person has two sets of DNA. The story says it is possible for a Chimera to have different sets of DNA in different body parts. This can cause complication for body identification, DNA typing for organ transplants, crime investigation, etc. Researchers have no idea how common this is, but suppose that it is a reasonable percentage of all fraternal twin pregnancies, which would mean millions worldwide. No text version. NPR often doesn't publish one. "
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Chimera Twins Story

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  • by afex ( 693734 ) on Monday August 11, 2003 @09:56AM (#6665538)
    so now when your liver commits a crime, it can be convicted seperately?
  • Hmm (Score:5, Funny)

    by pantycrickets ( 694774 ) on Monday August 11, 2003 @09:56AM (#6665543)
    I would like to be able to decide which of the two sets of DNA are set as 'active' at a given time. That would be nice for things like murdering my wife and whoever she is sleeping with outside of our house, and then getting away with the crime.

    If the DNA don't fit.. well.. uhh.. ahh shit.
    • Re:Hmm (Score:5, Interesting)

      by Zachary Kessin ( 1372 ) <zkessin@gmail.com> on Monday August 11, 2003 @11:21AM (#6666496) Homepage Journal
      Well if you are a guy, it would still be easy to get a DNA match, as the Y Cromisome comes only from the father with no recombination, so that will be uniform. Even if other stuff won't be. And since both sets of DNA come from the same parents they are going to look rather similar. More so now that labs know to look for this stuff.
      • Re:Hmm (Score:3, Interesting)

        by parnasus ( 321445 )
        Not to be totally pedantic, but being fraternal twins could mean that two fathers impregnated two eggs at nearly the same time. If it were possible for these two zygotes to merge, which I _highly_ doubt, then the resulting Chimera twin could have seperate Y-chromosomes from two fathers.
  • by hard2spell ( 692598 ) on Monday August 11, 2003 @09:56AM (#6665544)
    "My evil twin brother did it. Honest."
  • by Anonymous Coward on Monday August 11, 2003 @09:57AM (#6665549)
    The interesting thing is that since invitro fertilization has a much higher probability of twins (or more), chimeras will become more common.

  • by whorfin ( 686885 ) on Monday August 11, 2003 @09:58AM (#6665562)
    This is perfect for /. It's impossible to RTFA
  • Looks like (Score:2, Interesting)

    we should study this so we can give different parts of ourselves different DNA. If it is to be appropriated as a universal identification and control technology, we have to give it up if we want to remain sovereign. It is not that far away to have DNA identified radio tagging of people and, thus, near-absolute control.
    • Ooh, yes, such scary prospects. Perhaps eventually we can have stealth-DNA installed that morphs constantly to avoid detection.

      But maybe that's not such a good idea... if you can't quite reach your beverage, you could suddenly evolve into a creature with far longer arms, but it would probably be quite incapable of drinking it.
  • Heehee (Score:5, Funny)

    by Anonymous Coward on Monday August 11, 2003 @09:58AM (#6665568)
    No text version. NPR often doesn't publish one.

    Oh ho ho, methinks they'll change their mind very shortly.
  • Odd (Score:2, Interesting)

    by Anonymous Coward
    Doesn't DNA to some extent at least determine blood type? Would it be possible to have two blood types? Surely not, but as I do not have any way to listen to the link I will never know until some kind soul gives us the gist of it.
    • Re:Odd (Score:5, Informative)

      by Hentai ( 165906 ) on Monday August 11, 2003 @10:04AM (#6665644) Homepage Journal
      Well, IANAMB (I am not a molecular biologist), but I would assume that if the blood or tissue types were incompatable, the embryo would very quickly become non-viable, and the body would take care of it in the normal way (remember - only about 15% of all inception results in birth; the rest are spontaneously aborted.)

      I would imagine that the number of viable chimeric embryos is much lower than the total number of chimeric embryos; in fact, you could probably graph something like an inverse logistic curve of surviving chimeric embryos vs. days of pregnancy.

      • Re:Odd (Score:5, Interesting)

        by MadBiologist ( 657155 ) on Monday August 11, 2003 @10:13AM (#6665752)
        Finally!!!!! I can say IAAMB! I am a Molecular Biologist! Yeah ME!

        Now that I've got that out of the way... I'd say that quite often since differentiation of cell occures very early on, and that often the other allele in the pair is inactivated, it may be that one tissue type is derived from the one set of genes, and another type is derived from the other set of genes. That person may be a a higher risk of developing auto-immune diseases. Your proposition of spontanious abortion is quite possible... but remember Jurassic Park (life will find a way!).

      • Re:Odd (Score:3, Funny)

        by niko9 ( 315647 )
        Well, IANAMB (I am not a molecular biologist), but..

        Well, IANAAA (I Am Not A Acronym Abuser) but what was the point of you using an obscure acronym if you had to spell it out for everybody anyways? ;) /me make jokey joke/
    • Re:Odd (Score:3, Informative)

      A good resource about Identical v. Fraternal twins [about.com] states that fraternal twins develop when two separate eggs are fertilized and implant in the uterus. The genetic connection is no more or less the same as siblings born at separate times. They may look alike, or they may not.

      Chimera twins would contain both complete sets of "sibling" DNA, which could theoretically be female and male DNA combined, let alone multiple blood types.

      One might assume that multiple blood types would result in a (naturally) aborte
    • Re:Odd (Score:3, Interesting)

      by squarefish ( 561836 ) *
      Listen to it, it's very interesting. Basically the woman they interview had a kidney issue and needed a donor- when they tested her sons they said that it was impossible for them to be her sons. her blood type is from one egg and other parts of her are from the other egg.

      A detective talks about the possiblity of someone like this commiting murder where there is a blood sample left at the scene, but when they take a swap sample from the inside of the suspects mouth it shows a completely different dna.
    • by Tsu Dho Nimh ( 663417 ) <abacaxi@hotmail.cPOLLOCKom minus painter> on Monday August 11, 2003 @11:03AM (#6666259)
      "Would it be possible to have two blood types? Surely not, but as I do not have any way to listen to the link I will never know until some kind soul gives us the gist of it."

      IANAL, but IUTWIBB ... I used to work in blood banks doing crossmatches. A small number of people have two different ABO blood types. They are not "AB", they have some red blood cells that are pure "A" and some that are pure "B" and that is violating Mendelian genetics. The same mechanism that creates this could easily create other "blood chimeras" with the other several hundred lesser-known blood types. And a third mechanism (sex chromosome abnormalities) can create a kind of blood chimera that has nothing to do with twins.

      Apparently, most of these blood chimera individuals shared a blood supply with a non-identical twin before birth (the cells that make blood and populate your bone marrow float around the fetal blood supply while waiting for bones to develop to give them a place to settle, and the placentas and their blood vessels can merge without producing conjoined twins). In some cases, people are unaware that they had a twin because he or she died early in gestation and was spontaneously aborted (or disintegrated by the mother's defense mechanisms, or walled off in the mother or living twin). They show up in the National Enquirer when someone is operated on for a cyst and it has bits of the encysted twin in it.

      As many as 8% of non-identical twins may have chimeric blood. Some people are microchimeric--they have a small amount of blood of a different type in their system that has persisted from a blood transfusion or passed across the placental barrier from their mother before birth.

      "Blood chimerism" does NOT cause a problem for the person with the chimerism as far as receiving blood in a transfusion ... they will tolerate any phenotype they possess if you transfuse it - they have had it since they were fetuses and it is "self" in the immunological sense of the word.

      It can, however, be hell on blood banks trying to figure out what the heck is wrong with the blood during the initial typing and screening in a transfusion where the blood chimera is the donor. The potential recipient is not at risk because the tech says &^$^$#%@!!!, sets the donor unit back in the frig with a "do not use" note and sends it off to a research lab to find out what's going on. That's how you usually find blood chimeras and new blood types ... anomalous results in what should be a routine crossmatch.

  • by Thinkit3 ( 671998 ) * on Monday August 11, 2003 @09:58AM (#6665577)
    One of the X chromosomes is mostly disabled a little bit past conception (after the cells have divided a good amount though). However, which one is disabled is random at this time, which means different regions of the body derived from the original cell will have different X chromosomes disabled (into what's called a Barr body). This is all very screwy which is why females are very screwy.
    • by johnstein ( 602156 ) on Monday August 11, 2003 @10:06AM (#6665668) Journal
      This isn't directly related to what you said. but what happens if the fraternal twins that merge to become a single chimera twin are male and female? is this a possible explaination for hermaphrodites?

      Again, as I said elsewhere in another reply to this article. I am not a biologist, please be kind if this question has an obvious, or easily googlable, answer. :)

      -John
      • by wwest4 ( 183559 ) on Monday August 11, 2003 @10:12AM (#6665736)
        they mention this in the audio. apparently chimerism can manifest itself in a hermaphroditic fashion - they mention a (mostly) male chimera who apparently had ovarian tissue.
        • a (mostly) male chimera who apparently had ovarian tissue

          That would be a pretty freaky thing to discover about yourself. "Egad, I'm part female!" Gives a whole new meaning to, "getting in touch with your feminine side".

      • by Tsu Dho Nimh ( 663417 ) <abacaxi@hotmail.cPOLLOCKom minus painter> on Monday August 11, 2003 @11:27AM (#6666545)
        "is this a possible explaination for hermaphrodites? "

        No. Most hermaphrodites have DNA for one person - not two distinct cell populations from two separately fertilized eggs.

        Usually cases of "ambiguous gender" are the result of "testicular feminization", [nih.gov] ... genetically they are XY males, but because of an inherited trait on the X chromosome from their mom, they develop physically as female ... partially or to the extent that only their gynecologist could tell the difference.

        The two I remember from doing lab tests in a fertility clinic were very "female" looking. And no, we didn't say "guess what, you are really a man" when the chromosome testing came back because they aren't. The default state for humans is female unless testesterone is produced by the fetus AND the fetus responds to it.

    • The Y chromosome is pretty screwy [nature.com] in its own right.
  • Oh God... (Score:3, Funny)

    by mschoolbus ( 627182 ) <travisriley@@@gmail...com> on Monday August 11, 2003 @09:59AM (#6665583)
    And I thought images were bad when getting /.ed...
  • by Blackbox42 ( 188299 ) on Monday August 11, 2003 @09:59AM (#6665585)
    Any known birth defects/oddities arrise from this which manifest themselves in the physical sence? IE if your trying to test someone's DNA and realise they have blond hair on one half of there skull and black on the other you would know something was up.
    • by larkost ( 79011 ) on Monday August 11, 2003 @10:23AM (#6665867)
      The main thrust of the segment is about a woman who was told that her children could not be hers according to a blood typing. What was eventually discovered was that she is a Chimera, with the blood and eggs stemming from two different genetic strains (they would have been fraternal twins).

      • Oh, that woman. She is a "blood chimera" ... the red blood cells in her body have a population from her and one from her twin because of merged blood vessels in the placentas. This can sometimes give some misleading tests when ordinary ABO/rH testing is used. She was not a "tissue chimera", which would be an individual with mixed populations in the other tissues, such as ovaries, skin, heart, etc.
    • by Blue Stone ( 582566 ) on Monday August 11, 2003 @10:26AM (#6665906) Homepage Journal
      I know a girl similar to that - collars and cuffs don't match.

      I never realised she was a chimera!

    • by geoswan ( 316494 ) on Monday August 11, 2003 @11:42AM (#6666715) Journal
      There was a brutal serial killer in Russia, or maybe the old Soviet Union, who proved very difficult to catch, because DNA tests of his blood and semen didn't match. At the time I wondered how his DNA could fail to match. I guess this could be the explanation.

      Did an anomalous genotype contribute to his mental pathology? No obvious mechanism comes to mind.

    • by LenE ( 29922 ) on Monday August 11, 2003 @12:28PM (#6667193) Homepage
      More often than not, things don't go right.

      Everyone has heard of Downs syndrome, when a child has an "extra" chromosome. Well, think of having twenty three extra pairs.

      I am a fraternal twin, and I don't know if I am a chimera or not, but my wife and I have had trouble with a similar situation of too much DNA. Last year, we had a molar pregnancy.

      "What is that?" you may ask. A molar pregnancy happens when an egg is fertilized, but no baby is formed. It happens when the egg "looses" the genetic information from the mother (complete molar), or has three sets of chromosomes (69 total, partial molar). Molar pregnancies are about 1 in 1500 births, with 98% of those being the complete type.

      Either way, it is a horrific experience, and should be considered cancerous. The mother's hormone levels will climb to dangerous levels as the mass of cells that should have been an embryo rapidly grow and divide inside the womb. She will become extremely pregnant, without a child, and morning sickness becomes a 24 hour a day nightmare. Relief only comes with complete removal of all molar tissue. After this, the mother has to be monitored and be "pregnancy free" for a year, to tell if any of the molar tissue has become cancerous.

      Our case was a partial molar. If things would have gone right, we would now have a set of identical twins, but it didn't. DNA is a funny and powerful thing and too much is never good.

      -- Len
  • by DangerTenor ( 104151 ) <pmhesse2@gem i n i s e c urity.com> on Monday August 11, 2003 @10:00AM (#6665595) Homepage
    O.J. is INNOCENT! It was my.... uhh.... other DNA...
    • I realize you're making a joke, but Chimera's would have different DNA in different parts of the body. A swab from the mouth might have different DNA then a blood sample. However, if there was a match, this would still indicate that the person who gave the sample and the sample found at the scene were almost certainly the same person.

      A Chimera would create a false negative, because the DNA extracted from the cells in the mouth would not match the DNA of the blood at the scene.

      It might be a best practice t
  • Complications (Score:5, Interesting)

    by Upright Joe ( 658035 ) <uprightjoe@nOsPAM.gmail.com> on Monday August 11, 2003 @10:00AM (#6665598) Homepage
    The story says it is possible for a Chimera to have different sets of DNA in different body parts. This can cause complication for body identification, DNA typing for organ transplants, crime investigation, etc.

    Wouldn't this cause complications a little more important to the individual than those listed? Like say, stuff not fitting together right? I mean, I wouldn't want to try and build a working car from half Ford Explorer parts and half Ford Focus parts.

    I wonder how many people with this condition die before birth or at a very young age.
    • ONE PIECE AT A TIME
      Written by W. Kemp
      Recorded by Johnny Cash on 3/5/76
      Number one - County Chart; Number 29 - Pop Chart

      Well, I left Kentucky back in '49
      An' went to Detroit workin' on a 'sembly line
      The first year they had me puttin' wheels on cadillacs

      Every day I'd watch them beauties roll by
      And sometimes I'd hang my head and cry
      'Cause I always wanted me one that was long and black.

      One day I devised myself a plan
      That should be the envy of most any man
      I'd sneak it out of there in a lunchbox in my hand
      Now ge
    • 1 Car, 1 Part Source (Score:5, Interesting)

      by Mars Ultor ( 322458 ) on Monday August 11, 2003 @10:09AM (#6665704) Homepage
      The human genome isn't like the automarket...That is you're still building 1 car, but all the parts can be slightly different, but come from 1 supplier. After all, in a normal diploid animal (ie. humans) half of the chromosome content is from the mother, the other half from the father. As far as liver, heart, skin, etc. all working together, there is no problem with this.

      There is a problem though with the immune system. Since each organism's cells contain a unique combination of cell surface receptors that let's their body know the difference between "self" and a bug or virus, then depending which copy of DNA founded the cells of the thymus (where "self" is first determined), a chimera's immune system could see cells with the other DNA set as foreign - causing a massive systemic allergic reaction. The good news is that chimeras with this problem would spontaneously abort within the first few months of the pregnancy, so if a chimeric human is born, they probably don't have to worry to much about such genetic mismatches.
      • by baz00f ( 520771 ) on Monday August 11, 2003 @11:34AM (#6666630)
        Actually, as the chimeric embryo develops, the immune system would become tolerized to ALL self-antigens present. This is part of the normal development of a young immune system. The process is called "anergy", which makes immune cells unresponsive to self antigens. Since the two selfs are merged earlier than when the immune system develops, I doubt that autoimmunity is a problem.
      • The immune system will tolerate any antigens that it is exposed to at an early stage of fetal development. At a point that varies with each species, the immune system appears to take an inventory of "my cells and their surface antigens" and from then on it will attack anything not recognized as "self".
    • The transmission was a '53
      And the motor turned out to be a '73
      And when we tried to put in the bolts all the holes were gone.

      So we drilled it out so that it would fit
      And with a little bit of help with an A-daptor kit
      We had that engine runnin' just like a song
      Now the headlight' was another sight
      We had two on the left and one on the right
      But when we pulled out the switch all three of 'em come on.

      The back end looked kinda funny too
      But we put it together and when we got thru
      Well, that's when we noticed that we
  • It's not uncommon (Score:5, Interesting)

    by Anonymous Coward on Monday August 11, 2003 @10:00AM (#6665600)
    Nature published a short article on this a couple of years ago that we covered in our Journal Club meeting at my lab. The only one people detect right now are chimeric male/female twin pairs because its so easy but they had lots of cool shots under UV light where you can actally see like tiger striping of the two chimeric skin types. That was my favorite part.
  • by Blangopolis ( 695958 ) on Monday August 11, 2003 @10:01AM (#6665605)
    Anther great aricle about Chimera twins that I was reading eariler is here. [medterms.com] Man this stuff is really interesting. It actually says that about 8% of non-identical twins are chimera twins. That's actually pretty high.
  • by zubernerd ( 518077 ) * on Monday August 11, 2003 @10:01AM (#6665611)
    Since NPR only provides an audio link, here are some text sites with info on chimeric twins (genetic mosaics).
    [Genetic Mosaics] http://users.rcn.com/jkimball.ma.ultranet/BiologyP ages/M/Mosaics.html [rcn.com]
    Google search for Genetic Mosaics [google.com]
    And for the non-biologists [uiuc.edu]
  • criminal uses? (Score:4, Interesting)

    by johnstein ( 602156 ) on Monday August 11, 2003 @10:02AM (#6665622) Journal
    DNA typing for... crime investigation

    Interesting phenomena in itself, but I wonder if there are people who would (or already) exploit this sort of pseudo-anonymitity. Does anyone know how far this dual-DNA goes? can individual hairs have differing DNA? or will the blood have different DNA than the hair or skin? (I am not a biologist, so please be kind regarding these questions)

    -John
    • Re:criminal uses? (Score:2, Informative)

      by Anonymous Coward
      it'll be cell-by-cell initially, although as the fetus grows the initial cells will divide and give patchyness

      RE the Ford assembly issues discussed above, no problem at all unless the genomes conflict (i.e. one is saying "we're male" and the other says "we're female") - we're talking adaptive self-assembly here, the parts remake themselves as necessary. If you have a functioning immune system you're partly chimeric anyway, as (the short version) your immune cells mutate themselves randomly to be able to e
  • Does this mean... (Score:4, Interesting)

    by Alkarismi ( 48631 ) on Monday August 11, 2003 @10:03AM (#6665626) Homepage
    You can reconstitute the absorbed brother/sister through cloning the right cell?

    Could he/she then sue their sibling for attempted murder?
  • by Microsift ( 223381 ) on Monday August 11, 2003 @10:03AM (#6665632)
    Why not try this, turn on the radio, the story should be on again shortly after 8:30 PDT.

    No need to slashdot when the show is still available over the air.
  • by UncleBiggims ( 526644 ) on Monday August 11, 2003 @10:05AM (#6665657)
    In Greek mythology the Chimera was part lion, goat and serpent. This is why people with organ or limb transplants are sometimes referred to as a Chimera. So my question... do these people also present the same identification complications?
  • to take multiple DNA samples from a suspect.

    hair, blood, cheek, and perhaps ejaculatory(if it is a male)

    then compare them, if they al match, then the DNA should be considered accurate.
  • by swb ( 14022 ) on Monday August 11, 2003 @10:06AM (#6665675)
    You know the people I'm talking about, the ones whose bodies are somehow demented and just don't seem to fit together. Torso too big for the legs,legs too long for the torso, head too big, and so on.

    Probably not, but there's got to be an explanation for this phenomena.
  • When I heard the story this morning, I thought of bone marrow transplants. In that case, aren't you getting someone else's blood-generating cells? And wouldn't your blood cells then contain someone else's DNA?

    It seems like they'd make a Law & Order or CSI episode from this: a career criminal arranges to get a bone marrow transplant from someone whose DNA is known to authorities, but who hasn't yet been apprehended (ooh, big word!). Then, the real bad guy can leave all the blood he wants at the crime
  • by niko9 ( 315647 ) on Monday August 11, 2003 @10:08AM (#6665695)
    There's an organizitaion called the The Innocence Project [innocenceproject.org] headed by Barry Scheck which prides itself on freeing prisoners who didn't have the technology of DNA testing avaible to them during their trials.

    In light of this article, I wonder how many guilty people have been set free. I'm sure there are guilty parties that proclaim their innocence and see no harm or foul in having the DNA testing done by said non profit organization, in hopes of some fluke in their favor.
  • by Alcimedes ( 398213 ) on Monday August 11, 2003 @10:08AM (#6665696)
    It's just his white Chimera brother finally coming out after all these years.
    • Sometimes somebody actually posts something that deserves +5 funny.
    • by Herg ( 564957 ) on Monday August 11, 2003 @10:25AM (#6665897)
      Don't you mean Chimera sister?
    • by cheesedog ( 603990 ) on Monday August 11, 2003 @12:59PM (#6667482)
      Funny. Truly.

      So it is with some reluctance that I have to be a wet blanket... I know a sweet little girl who suffers from the same pigmentation disease as Jackson. It is called vitiligo, and although not health-threatening, it can be somewhat difficult for children who get labeled as "different" because of the light splotches that appear on the skin, and then spread. When it grows to cover more than 50% of the body, many opt to bleach the remaining <50% so that they are at least all one tone. I believe such is the case with Jackson.

      Of course, it doesn't help that Jackson is a freak in many other ways, but there are thousands and thousands of people in this country, many of them children, who suffer from this condition without being freaks in any other way.

      They are lucky when compared to the diseases that afflict many other people, but the disease is relatively unknown, so I thought I'd add a few words here in their defense (but not in Jackson's -- he's on his own :)

  • two sets of dna produce two different sets of oragn, tissue, cell, antigens that identify these parts as belonging to body..

    Chimera embryo would not survie due too much body rejection of the parts of body that has the different dna..

    The only case where thsi cannot happen and regualr occurs is the difference between human cell dan..or human genome nuclear and mitochrondia dna which produce no antigens but is diferent from the nuclear dna in that is the mother inherited mitochroindia dna form mother of the
    • by mikeee ( 137160 ) on Monday August 11, 2003 @10:31AM (#6665961)
      Not a problem in this case; the immune system hasn't 'initialized' at that point, and so would imprint both types as self when it comes online.

      This is why people are interested in freezing fetal blood samples; the theory is that you keep a backup of the immune system install media to reinstall if it goes bad. Um, except that we have no idea how to do that yet... works in theory, though.
  • Maybee the story of (Score:2, Interesting)

    by KMAPSRULE ( 639889 )
    Dr. Jeckle(sp?) and Mr. Hyde isn't too far fetched after all. The "formula" Jeckle drinks to become Hyde simple turns on the alternate DNA sequence.
  • But here is an artists sketch [lysator.liu.se] of what one of these Chimera twins might look like.
  • I've been told that the propensity to produce fraternal twins is an inherited trait, unlike identical twins. Is this Chimera twin state also inherited, or is it a random mutation?
  • by nizo ( 81281 ) on Monday August 11, 2003 @10:17AM (#6665794) Homepage Journal
    Am I the only one who read the title and thought, "Finally! All this messing with genes has produced something useful, a fire-breathing Chimera with a lion's head and a goat's body"? On a more serious note, the nature article in a similiar vein is here [nature.com].
  • by Q-Branch ( 554342 ) on Monday August 11, 2003 @10:25AM (#6665887)
    Slightly OT:

    Here [bbc.co.uk] is a pretty freaky story of a boy who seems to have assumed his twin in the womb. No one knew until when,at age seven, he had a stomach ache and surgeons removed his brother.

  • by Anonymous Coward on Monday August 11, 2003 @10:28AM (#6665933)
    While I don't know for sure if I am a chimera, I was born with XX/XY sex chromosomes, something I only found out in my early 20s.

    For many of us born this way we don't appear to be completely male or female and like most I was surgically "repaired" very soon after birth. This means I had what appeared to be testicles removed, testicles which MAY have permitted me to have children one day. Part of my body was stolen because I looked different. I was raised female, always felt that didn't quite fit, and it took me a lot of messing through courts to obtain my birth records. As I am now I have to settle with knowing where I fit originally, why I am like I am, and can accept living as a mostly normal female. By nature however, I was born part male part female. That's me. The chance to live and develop naturally was stolen from me.

    It's fucked. Science continues to find so many variations on human development but society so often manages to force decisions on people. How odd that I was considered unnatural enough when I was born that doctors decided surgery was the only acceptable option, when my birth and very existence is just one more facet of nature.

    For more info on how intersexed kids (chimeric or any other variation) are treated, see isna.org [isna.org]
  • by b-baggins ( 610215 ) on Monday August 11, 2003 @10:35AM (#6666007) Journal
    This link has some good information on Chimeras. Including a discussion of the lady featured in NPR.

    http://users.rcn.com/jkimball.ma.ultranet/Biolog yP ages/M/Mosaics.html
  • It doesn't take "chimerism" to get this effect. The well-known variations in the number of sex chromosomes can also do it, and they can happen in the cell division process.
    Normal male = Xy (any extra "X" are abnormal, but even a XXXXy is still male - all but one X gets deactivated - but usually has serious medical problems). Normal female = XX (extra "X"s do not create supermodels, it creates medical problems)

    Take a look at any calico or tortoise shell cat. What you are seeing is the result of random deactivation of one of the X chromosome early in the development of the embryo, and the random appearance of the colors (black or orange) on that chromosome. Humans have few easily testable traits that are testible for chimerism: one blood group is all I can think of at the moment, that "lives" on the X chromosome.

    For calico or tortie males (yes, they exist, and no they are not valuable) the division between the colors is a good indicator of how badly screwed up their sex chromosomes are. A male that is mostly orange with one small black patch probably acts like a tomcat and will show very few cells of the XXY pattern, and might even have that abnormality limited to that spot. One that is well-mottled with black and orange is probably not interested in breeding and will show mnay more abnormal XXY cells.

    In order to test this for the possibility to screw up DNA identification, they could start by testing the known chimeras - cats.

  • A Tetragametic Human (Score:3, Informative)

    by gooru ( 592512 ) on Monday August 11, 2003 @10:59AM (#6666206)
    Reading the post but refusing to listen to the audio clip got me interested in searching Google for all of this. I came across one link in particular, which is very interesting:

    Genetic Mosaics [rcn.com]

    The writer discusesses a tetraparental mouse and a tetragametic human.

This is now. Later is later.

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