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Biotech Science

Semi-Identical Twins Discovered 224

daftna writes in with a story from Nature about a pair of twins who are neither identical nor fraternal: they are semi-identical. Researchers discovered twins who share all of their mother's DNA but only half of their father's. Both children are chimeras — their cells are not genetically uniform, but include a mix of genes from two separate sperm cells that fertilized a single egg. This is, apparently, not as rare as one might think; but the resulting fetus is rarely viable. This report marks the first known incidence of two half-identical twins resulting from a double fertilization.
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Semi-Identical Twins Discovered

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  • by Marxist Hacker 42 ( 638312 ) * <> on Tuesday March 27, 2007 @08:09PM (#18509737) Homepage Journal
    We're finding new chimeras every day, now that DNA testing is becoming more common. Discovery Health even had a program where genetic testing showed a mother's children to be the product of her BROTHER and her husband; though she had no brother. Turned out she was a hermaphrodite- some of her cells, including her EGGS, were male- a fraternal twin that had been absorbed early in the gestation process.
  • This isn't new... (Score:5, Interesting)

    by 7Prime ( 871679 ) on Tuesday March 27, 2007 @08:29PM (#18509883) Homepage Journal
    Maybe this was slightly different, but I knew two guys back in high school who were genetically half-identical twins. I guess the condition was caused by the polar body (which normally disentigrates) containing enough cytoplasm to sustain itself, and thus allowing it to be fertilized by a sperm other than its pair. They refered to this as "Polar Body Twins". It is extremely rare, but not unheard of. Furthermore, they really looked the part, being much closer in appearance than fraternal twins, but being subtley different from identical twins.

    There seems to be a hot debate over the possibility of this happening. Some scientists fully support the notion that this happens, while some have rejected the notion altogether, citing that polar body's don't "normally" contain enough cytoplasm to sustain themselves. But this sounds like a rediculous arguement, to me, since the exact amount of cytoplasm that is both required for fertilization, and the exact amount that a polar body usually contain, very wildly.

    Unfortunately, it's very difficult to confirm whether or not this occurs, since percentage of difference in genetics between both fraternal twins and polar body twins is not exact. Polar Body twins will always contain between 50% to 100% of the same genentics (averaging at 75%0, where-as fraternal twins could be anywhere between 0% to 100% similarity. So, my friends will never actually know whether they developed from identical zygotes, but their genetic makeup was similar enough, that many doctors speculated that this was the case.
  • by Grishnakh ( 216268 ) on Tuesday March 27, 2007 @08:33PM (#18509911)
    This is the second comment along these lines. I don't see anything in TFA indicating that the two sperm cells are from different men; they're just different sperm cells (which all are different, even from the same man, since they only contain half the man's genetic code).

    However, I have heard of women having fraternal twins by two different men. So "semi-identical" twins by two different men would be an extremely rare and interesting bit of news, since the twins would each have genetic material from both fathers.

    Maybe some women should try for this to achieve notoriety and advance the cause of science...
  • by Anonymous Coward on Tuesday March 27, 2007 @08:35PM (#18509929)
    Could a similar event lead to a virgin giving birth? News of such an event could be of Biblical proportions.
  • Re:Serious question (Score:5, Interesting)

    by tloh ( 451585 ) on Tuesday March 27, 2007 @08:41PM (#18509991)

    talk about deja vu!

    Some time ago, I wondered about the exact situation this article raises. &cid=10879347 []

    At the time, it fascinated me because it occured to me that you could have twins which share a maternal set of chromosomes but have one sex chromosome from the father be an X for one of the siblings and the other be a Y.

    In other words, almost identical twin brother/sister pair! One wonders how much of gender is actually in our genes. Well, to have a pair of individuals share so much with the exception of the sex chromosomes - it becomes more reasonable to do an actual comparison. (I am aware there is still lots of room for genetic variation from the rest of the father's somatic set) I don't know how scientific it would be, but as a thought experiment, I wasn't to concerned about it at the time I posted it.

  • by countach ( 534280 ) on Tuesday March 27, 2007 @09:10PM (#18510243)
    One wonders what would happen with child support payments if the two sperms came from a different father. I doubt the rules and regulations know how to deal with that one.
  • by iamacat ( 583406 ) on Tuesday March 27, 2007 @10:17PM (#18510637)
    This is the least of these kids problems. One of the kids has genitals which are in between penis and vagina. Both have inconsistent genetic makeup which is bound to cause health or at least fertility issues. Imagine living a life where you are called "a very special and wonderful person", but no personal life or even ability to enter either public restroom without people looking at you dubiously.
  • by boingo82 ( 932244 ) on Tuesday March 27, 2007 @10:42PM (#18510801) Homepage
    Your description of the show is VERY inaccurate - the main person featured in the show, Lydia, was not a hermaphrodite. She did not have male eggs. She did not have male cells.

    When she was DNA tested to receive welfare, the DNA indicated that her children weren't hers - but the mother would've been someone with similar DNA *like a brother* of hers.

    Somehow you took that to mean that she had hermaphroditism, which would have made her infertile. That's pretty illogical - how the hell does a person have male eggs? And how would they think that her kids had been fathered by two males? They didn't.

    A more accurate summary of the show is here. []

  • Re:This isn't new... (Score:2, Interesting)

    by DavidTC ( 10147 ) <<moc.xobreven> ... .vidavsxd54sals>> on Tuesday March 27, 2007 @10:43PM (#18510805) Homepage

    While in theory siblings can share 0% genetic code (At least, 0% of the genetic code that actually differs among humans.), male siblings must share at least a little. There's only one possibly source for the Y chromosome.

    Incidentally, this article is talking about polar body twins, but ones that 'merged' and then 'unmerged', or, more technically, separated incorrectly. Instead of splitting when first fertilized, they split later, along non-genetic lines.

    This resulted in two people who had both sets of genetic codes, in fairly random cells. This is called a chimera, or, rather, two chimeras, and usually results in's like doing random transplants between people on the street with no regard to the immune system or blood types. Usually part of the body ends up attacking another part.

    When they do live, they usually have odd 'banding' where their skin changes color and their eyes can be different colors. (Note: Eyes can be different colors for other reasons.) If they are a mix of XX and XY, they not only can be intersexed, they can be fully functional hermaphrodites, with both ovaries and testicles, and all the genitalia that goes with both of them. (Although thanks to weird hormones they are unlikely to produce children either way.)

    These kids are 'half-chimeras', in that the genetic code they got from their mother is the same throughout, so only half of the code differs. I seem to recall that most chimeras who live are 'half-chimeras', which makes sense. These two are just odd in that they split into twins, which is mildly ironic in that they 'should' have been polar body twins in the first place, but didn't become twins at that time, and then, later on, they did split up randomly.

  • The new testament wasn't translated from Hebrew, was it?
  • by Moraelin ( 679338 ) on Wednesday March 28, 2007 @02:51AM (#18512195) Journal
    Here's one thought for you: Splash Conception []. A.k.a., anal sex is not 100% reliable as birth control. It only takes one drop of sperm on reaching the vulva, and the spermatozoa's mobility takes it from there.

    Then there are things like an elastic hymen, and various other fun ways to end up pregnant while technically a virgin.

    And to make it even more fun, think this: they later had to invent an explanation for exactly this kind of thing, namely the succubi and incubi. Virgin virtuous girls (yeah right) were supposedly impregnated by incubi. You don't invent a whole explanation for something that never happened ever since. So basically they knew it happened more than once, and in fact it happened again and again.

    So here's what _really_ makes me wonder: why is everyone pretending that something happening all the time is a one-time divine miracle? I mean, hello? It's like proclaiming that there is only one Car made by God himself, and steadfastly refusing to acknowledge all the other cars around you. They can't exist, because God said they don't exist.

    I don't know, it's basically fascinating how people can basically force themselves in a thoroughly schizophrenic frame of mind where they believe two completely opposite things at the same time. E.g., simultaneously that (1) Mary's virgin conception was such a unique and inexplicable thing that can only possibly be explained by divine intervention, yet at the same time (2) thousands of other virgin girls got pregnant too, e.g., via incubi. Hello? How can one have unyielding faith that something is unique and non-unique at the same time? Or that it could have been possible only by divine intervention, yet at the same time the same happens without divine intervention all the time? (E.g., via demons.) Mind boggles.

    Or maybe that's the ticket. The more absurd and illogical a religion is, the more people will rabidly fight against anyone saying otherwise, because it trips their own insecurity and doubt. Better burn the heretic before he manages to make you think more about that.
  • by mazarin5 ( 309432 ) on Wednesday March 28, 2007 @03:36AM (#18512387) Journal
    Actually, the law should handle this quite well. In my state at least, paternity is established if the child shares 99% of particular markers with the potential father. In this case, one child would have 50% of Suzie's DNA and 50% of Steve's, while the other would have 50% of Suzie's and 50% of Joe's. The testing would clearly indicate which child corresponded to which father, and the law is based on that testing.
  • Re:On intersexuality (Score:1, Interesting)

    by Anonymous Coward on Wednesday March 28, 2007 @12:04PM (#18516469)

    I am intersexed; in my case they decided to remove my female bits when I was 10 months old, reroute my urethra and give me nice scarred junk. It's on my medical records and 'benign growths' and the hysterectomy is on my record as a "hernia." Locker rooms through Jr. High were absolute fucking hell I wish I could forget.

    Also, during Jr. High I was put on testosterone - I thought going to the doctor for "booster shots" every couple of weeks was just something people did, then when things began to happen I grew wise to it. I grabbed the vial, read the name, and looked the chemical up at the library afterward. When I realized what they were doing to me (it FINALLY dawned on me that I'm a hermaphrodite and I confronted my mom about it), I stopped cooperated. I wanted to reverse what was done to me, but my mom would not hear of it, telling me they made the decision they did for my own good, that I'll change my mind later, and so forth.

    The root cause in my case is CAH (congenital adrenal hyperplasia) - I lived with it for 30 years before being diagnosed. I've been to endocrinologists to get on hormones to become less androgynous (growing up and being asked "are you a boy or a girl" all the fucking time really fucking sucks. It REALLY fucking sucks). I was living with constant hunger pangs, thinking it was normal (when you have never known anything else you don't know any better, I know it sounds weird to you but take my word for it, I thought it was normal to always be hungry) so what I went by to know when to eat was I would get weak. Also, I had constant low-level kidney pain, and since it was always there, I didn't know any better. It turns out I was not eating enough cholesterol, so when I would wait to eat, I was going into adrenal crisis. I've lived with that pain and the migraines that come with salt wasting for a very, very, very long time and although the endocrinologists I've been to all remarked that my adrenal glands don't seem to be producing sex hormones correctly (no fucking shit sherlock) no other mention of it was made, and I wasn't tested for CAH. It took a friend who is also intersexed to clue me in (and explained that few endocrinologists have IS experience, and even fewer know how to deal with it correctly) and a physiologist friend of mine to confirm the diagnosis after research and tests.

    My parents have tried to bury it in the past and STILL want to keep it quiet, and I am now in my mid-30s. I will never, ever forgive the doctors who such made a decision (or more accurately coerced my parents into making what was for the doctors the most profitable decision) for me, without my consent. I am sick and tired of being androgynous, and while I appreciate that I am unique; literally one in a million, I will never, ever, ever forgive those doctors. If they were still alive today I would personally hunt them down and murder them, without any remorse whatsoever.

    Back when I had medical coverage, the insurance companies would not cover any surgeries (preexisting condition), and what pisses me the fuck off is that I know trannies who get surgeries approved (even cosmetic surgeries) without a bat of an eye. I still haven't had the work done; there is only one doctor who does SRS who would even agree to talk to me (funny, they'll cut off guys's weiners without batting an eye, but they will not reverse unconsented surgeries performed on intersexed folk?) but the pain I will incur from multiple skin grafts (what I have is too scarred to work with) is not appealing, and the amount of money it will take is just something I have not had, and don't know if I will ever have.

    Also I hate getting lumped in with trannies. I am not a fucking tranny. Do not lump me in with them; they CHOOSE to genderfuck; they were not born into it without a choice. Not every androgynous person you see is a goddamned tranny.
  • Re:On intersexuality (Score:2, Interesting)

    by wolfsdaughter ( 1081205 ) on Wednesday March 28, 2007 @05:21PM (#18520695)
    Obviously, IS is different than TG in a physical way.

    But can we be sure that the root cause for IS always completely different than TG?

    IS can be caused by different things, some of which could turn out to be the same sources influencing expression of TG, which might make physical expression (IS) and emotional/mental expression (TG) just different aspects of the same thing.

    I didn't think you were going out of your way to be hurtful, but it still stings.

    and yea, there are some trans people that I'm not comfortable around, probably for the some of the same reasons you.

  • Re:On intersexuality (Score:3, Interesting)

    by aebrain ( 184502 ) <> on Wednesday March 28, 2007 @09:20PM (#18523439) Homepage Journal

    Those of us who have experienced the hatred, the violence, the rape, the cigarette burns.... the usual stuff every transsexual boy or girl goes through should be kinder to those who are Intersexed. Remember, this woman was made transsexual at the point of a scalpel.

    I'm both Transsexed (as in "brain physically mainly of one sex, body physically of the opposite sex:"), and Intersexed. Androgen Insensitivity, Adrenal Hyperplasia, and a Leydig cell anomaly, not that I have any Leydig cells any more. I know what it's like to have to pretend to be one sex, even though I was the other, and do so with the additional handicap that the body wasn't 100% functional in either role, but a mixture. It was easier for me though, I had no surgical intervention, and Dr Suporn in Thailand has taken my sorta masculinised groinal area and made it indistinguishable from that of a natal female (AT LAST!).

    Those of us who are Intersexed should look at the latest Scientific and Medical Evidence that Transsexuality (as opposed to crossdressing etc) is just another Intersex condition, and no longer consider TS people psychos, freaks and weirdoes who we want nothing to do with.

    Wolfsdaughter, this person has had bucketloads of pain all their life. Unlike us, they could maybe have had a normal life in their actual gender, with children, but a surgeon's knife took that away. How can we blame them for seeing people with normal genitalia getting them re-shaped and made sterile, and thinking that we are wasting a gift they would have given anything for? Yes, her words were hurtful, but if anyone has a right to hurt us, she does. Not the "norms", the ones who stoned us or beat us with crowbars just because we "vibed wrong". So please, forgiveness. Yes, her remarks hurt me too, BTW, but no matter.

    Let's just make sure the World, the /. ers anyway, know we exist. That we are human. That the rate of transsexuality in the general population may be 1:3000 (not 1:30,000 as is usually stated) but in the InfoTech area it's more like 1:300, as we're good at it. Our brains are wired up differently, and in some ways, many of us are smarter than the average bear. Let the /. ers know that during their careers, they will see people like us. As the line in Transamerica goes, "we walk among you".

    And Please, Please, Please, as Transsexuals who know just exactly how much that condition SUX, stop the "genital normalisation" of babies until they've grown up enough to tell us whether they're boys or girls (almost always by age 7, often even by age 3). Because there is a difference, in the brain structure, and although there are people who can function in whatever role they're brought up in, for most of us it's hard-wired long before birth. Please let us stop the surgical creation of Transsexual babies.

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