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Biotech Science

Semi-Identical Twins Discovered 224

Posted by kdawson
from the my-brother's-a-keeper dept.
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 alcmaeon (684971) on Tuesday March 27, 2007 @08:09PM (#18509735)
    Subject says it all.
    • by maxume (22995) on Tuesday March 27, 2007 @08:11PM (#18509753)
      Problems with your sperm count? (lots of guys have more than, ya know, one. Harr).
    • by Anonymous Coward on Tuesday March 27, 2007 @08:49PM (#18510059)
      Inconceivable!
    • 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 Anonymous Coward
          but no personal life or even ability to enter either public restroom without people looking at you dubiously.

          I dunno about you, but when I go to the restroom, people usually don't see my weenie. And there's always the stalls to do your business, you know. Furthermore, if people really want this sort of thing "corrected", there are surgical procedures and drugs to make anyone clearly male or clearly female. As for medical risks, most people who are chimeras never seem to find out anyway.
        • On intersexuality (Score:5, Insightful)

          by asninn (1071320) on Wednesday March 28, 2007 @04:17AM (#18512609)

          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.

          Do you really think that this is the biggest problem intersexual people will ever face in their life? If yes, you seriously need to read up on these things a bit.

          First of all, as a disclaimer, I'm not intersexual myself, but I'm interested in inter- and transsexuality and know a couple of people who are. Most of the intersexuals I know had a gender surgically assigned to them after birth, too (female, FWIW; as doctors say, "it's easier to dig a hole than build a pole"). But you know what? Neither of them is happy.

          In fact, the *exact opposite* is true. *Every single* intersexual I've talked to or heard about has said the same thing so far - that doing so is, essentially, butchering, a traumatic experience that will haunt you for your entire life. Even in these times where sexual reassignmet surgery is not impossible anymore, the results are far inferior to anything that nature came up with (if you can even afford the whole procedure!), and the psychological problems associated with having your body mutilated after birth are just as serious.

          What really needs to be done when an intersexual child is born is really easy: bloody leave them alone. The child will eventually grow up and be able to make their own decisions; if they decide then that they really belong to one gender, it's not too late to do surgery etc.. What's more, it might well be that the child decides that they're really male - contrary to popular opinion, "intersexual" and "transsexual" do not mean "a guy who wants to become a chick".

          But there's also a decent chance that the child will say "I'm happy the way I am", and who's to say that that's not within their rights? If the only reason you can come up with is that there might be confusion over which restroom is appropriate, well... I'm sorry, but that isn't quite enough.

          What's more, when you're talking about things like restroom usage, you make a very fundamental mistake: you look at what other people and society in general will see the child as, rather than what the child themselves thinks. But it's the child who will have to live with their body; the idea that society has a right to say "you don't fit into our binary system, so we'll cut up your body and then pretend that you do (even though you really still don't)" is outrageous.

          FWIW, BTW, another fundamental mistake that's often being made is the assumption that it's even possible to reassign gender - that is, the actual gender that someone identifies as, as opposed to their physical sex. One of the reasons why intersexual people were mutilated in the past and raised as girls is that doctors (wrongly) believed that if you just cut off everything that was non-girly and if you just put the child into a dress and told them they were female, they'd really believe it and grow up as a normal, well-adjusted *woman* - but in reality, it doesn't work, and never has.

          Of course, I do understand that there are no ulterior motives - doctors, parents etc. really are trying to help intersexual children. But it's also important to realise that it's not working and that the only thing you're doing is CAUSING harm, not preventing it.

          So, although this has little do to anymore with the original TFA, just let me say this: leave intersexual children alone, and let them make their own decisions when they're old enough. Until then, be tolerant, be honest, explain to them why they're different, and explain that it doesn't make them worth less or anything like that. That's the ONLY way you can actually help them.

          • Re: (Score:3, Insightful)

            by master_p (608214)
            The problem is, how do you shatter absolutism in the minds of people? it is a proven fact that nature is not black and white, and there are many shades and colors in between. But most humans can not live comfortably in the chaos that nature is, preferring order in the form of binary systems: good and evil, male and female, white and black, cold and hot etc.

          • Re: (Score:2, Funny)

            by Knux (990961)
            First of all, as a disclaimer, I'm not intersexual myself, but I'm interested in inter- and transsexuality

            You mean like watching bizzar porn hu?
            Pervert...
          • by operagost (62405)

            But there's also a decent chance that the child will say "I'm happy the way I am", and who's to say that that's not within their rights? If the only reason you can come up with is that there might be confusion over which restroom is appropriate, well... I'm sorry, but that isn't quite enough.

            I have no idea what you're talking about.

            - Pat

          • by jafac (1449)
            I agree that sexual reassignment surgery is barbaric, and should never be done on an infant;

            I think that victims should not be haunted or troubled about the way that they have been reassigned. There's a lot of angst about it - but there's also a lot of evidence that sexuality, including the ability to reach climax, and the quality of the climax, is largely psychological. True - the damage to (or removal of) tissue with large amounts of nerve endings can be crippling. And the longings that one has for part
      • by Brad1138 (590148) *
        the two sperms came from a different father.

        Probably the different father would pay.
      • Re: (Score:3, Interesting)

        by mazarin5 (309432)
        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: (Score:3, Insightful)

          by countach (534280)
          No, we're talking about one child with 50% of Suzie, 25% Joe and 25% Steve.
          • by cayenne8 (626475)
            "No, we're talking about one child with 50% of Suzie, 25% Joe and 25% Steve."

            I can't seem to get this outta my head...

            "So who da baby daddy?"

            :-)

          • by mazarin5 (309432)
            Note to self: clicking the link does not count as reading the article. :)
      • Re: (Score:3, Informative)

        by niktemadur (793971)
        Similar (but not, ahem, identical) cases have popped up before.

        I remember reading a long time ago, in one of the Wallace/Wallechinski Book Of Lists, an article about a case in the seventies in Germany, more mundane in that two eggs were fertilized, so that the kids were not chimeras, but extremely weird in outcome, as the woman gave birth to two boys, one fully african and the other fully caucasian!

        I believe it's the only recorded case of two simultaneous fertilizations from different ethnic gene pools, but
        • by jpkunst (612360)

          the woman gave birth to two boys, one fully african and the other fully caucasian!

          Surely the boys must have been either half african and fully caucasian, fully african and half caucasian, or half african and half caucasian.

          JP

  • by Marxist Hacker 42 (638312) * <seebert42@gmail.com> 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.
    • 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.
      • by Starburnt (860851) on Tuesday March 27, 2007 @08:56PM (#18510127)
        More importantly, Slashdotters may now be able to reproduce.

        That could be of Biblical proportions.
      • Already happened. (Score:5, Informative)

        by gcnaddict (841664) on Tuesday March 27, 2007 @10:23PM (#18510665)
        It just hasn't happened in humans yet.

        http://news.bbc.co.uk/2/hi/science/nature/6196225. stm [bbc.co.uk]
      • by kestasjk (933987) * on Tuesday March 27, 2007 @11:33PM (#18511127) Homepage
        Are you calling the virgin Mary a hermaphrodite?! Blasphemy!

        As we probably all know 'virgin' was indisputably a mistranslation; the Hebrew for 'young woman' (almah) was translated into the Greek for 'virgin' (parthenos). I wonder why we all still refer to her as the virgin Mary, now that we know she wasn't (necessarily, to be absolutely pedantic) a virgin.
        • by Rolgar (556636)
          Christianity teaches that Jesus is the God-man. That is, his mother was human, his conception caused by the Holy Spirit, so that the mix of his divinity (Godness) and humanity has cured our humanity from some of its brokenness, and his death was the death of sin, and his rising from the third day was the defeat of our mortality that gives us a chance at eternal life. If he had a human father, that's not the case, Jesus wasn't God, and his death would not be sufficient to redeem humanity from sin. Some ind
        • Re: (Score:3, Interesting)

          by Boronx (228853)
          The new testament wasn't translated from Hebrew, was it?
          • by operagost (62405)
            No, but the prophecy from Isaiah was. Regardless, it is a lack of understanding of Jewish culture that leads to this debate; as a young woman was reasonably expected to be a virgin in that culture and "almah" assumed this, much as the somewhat archaic English word "maiden" does.
        • by JeanPaulBob (585149) on Wednesday March 28, 2007 @01:20AM (#18511735)
          No, "virgin" was not "indisputably" a mistranslation. And it is most certain that your "young woman" is a poor translation--to my mind, worse than "virgin".

          The issue is not with the New Testament; there is no question that Mary is reported to have been a virgin in the New Testament. The issue originates with the Septuagint, the Greek translation of the Old Testament produced by Jews before the time of Christ, and it has to do with the translation of Isaiah 7:14, an ostensibly Messianic prophecy. (The Septuagint was the translation used by New Testament writers.) It translates the Hebrew "almah" with the Greek "parthenos". Parthenos almost always means "virgin", while almah has a slightly different but overlapping semantic range. It's closer to "maid, unmarried girl, young woman of marriageable age". (Your "young woman" leaves out the unmarried/of marriable age implications.) Culturally speaking, an almah most likely would be a virgin--that would be the strong expectation, and it's enough to make "virgin" a connotation of "almah". While parthenos is not a precise translation, it is not a mistranslation. At the very least, not indisputably so. My goodness, man, just read the Wikipedia entry on almah and follow the references! This is not obscure information.

          Sure, if you limit the meaning of "almah" to "young woman", it makes for a better game of "Hee hee, look at the silly Christians," but if you're interested in honest scholarship, you'll have to open your mind a bit.
        • by Ravon Rodriguez (1074038) on Wednesday March 28, 2007 @01:52AM (#18511891)
          Turning water into wine, walking on water, bringing the dead back to life... and It's the translation of the word "virgin" that you have a problem with?
        • by rucs_hack (784150)
          we also still talk about parting the Red Sea even though it is now known to mean 'the sea of Reeds.

          I like the old testament though, it's cool the way archaeologists went round the world, bible in hand, and found all kinds of 'mythical' places were real. Mind you, I read it as a very old book, not as a guide to life or any such crap. Tried to read it in the Hebrew once, but I wasn't patient enough to learn all of the language.

          The new testaments a crock, it reads like a comic book.
          • Just like the way Schliemann went out and discovered Troy, proving that all of the events in the Illiad and the Odyssey were real, too.
        • Here's one thought for you: Splash Conception [wikipedia.org]. 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
          • A.k.a., anal sex is not 100% reliable as birth control.
            Ooops. Do I now need to worry about getting my boyfriend pregnant?
            • by Moraelin (679338)

              Ooops. Do I now need to worry about getting my boyfriend pregnant?

              Only if your boyfriend has a working set of ovaries, womb, and vagina. Note that it's a bit like the WoW equipment sets too: you need all pieces to get the big bonus. Just two out of three isn't going to do the trick.

              Also that's assuming that you are a man. Fucking someone up the ass with a dildo or strap-on, sadly, misses another piece of the equation, namely the sperm. I'm affraid you can't quite get the synergy effect without that part.

          • 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 an
          • by operagost (62405)
            Fortunately, believers don't lean only on the virgin birth as their basis for belief in the Christ. There are dozes of other prophecies put into play. Naturally, if you believe Jesus was God, you're going to surmise that God would have used divine methods for this purpose rather than having Mary anally raped.
            • 1. I didn't say (necessarily) "raped". Let's face it, since the dawn of time, a lot of men were curious about that. I can just imagine a caveman in a stylish sabertooth-skin loincloth pleading with his woman to let him try that way too. Note that I'm not saying it's right or wrong, just that it happens.

              And a lot do say "yes" at some point or another. I was reading a statistic about a decade ago, and IIRC about 50% of the polled women had taken it up that route in the USA, and it was raising well over 80% in
        • by master_p (608214)
          "Young woman" in those times meant the girl was a virgin.

          Of course it would really be good to be able to prove Mary was no virgin, because religion, as it is right now, causes more problems than it solves, but we have to be fair with the historical texts and recognize the fact that people were not so "accurate" back then.
      • by rrohbeck (944847)
        Virgins giving birth happen all the time.
        Did nobody tell you to be careful when, uh, fooling around?
    • Hate to be the party pooper, but do you have a link?
      • I searched for one. All I got was bloggers to the show. Perhaps you'll find something at Discovery Channel [discoverychannel.com], but as I can't see that from work, perhaps you'll do better than I did....
      • Re: (Score:3, Informative)

        by brunes69 (86786)
        I'll vouch for the parent, I saw the same show. But I think it was on TLC.
      • by Schemat1c (464768)

        Hate to be the party pooper, but do you have a link?
        I don't know if it's the same story but here's a link to a New Scientist [katewerk.com] story about Chimera's.
      • I saw this show too, about a year ago - it was the first thing that came to mind when I saw this article.

        Some of these women nearly lost their kids because they couldn't prove via DNA tests that the kids were theirs - child services thought they'd switched them at the hospital or something, even though the father was the father.

    • by good soldier svejk (571730) on Tuesday March 27, 2007 @08:38PM (#18509953)
      Chimerism is also a source of the exceedingly rare brindle coat pattern in horses. [aol.com] In such cases the different color hairs will have different DNA. In one case this caused two consecutive DNA sample sent to a lab for pedigree verification to return negative parentage for both the sire and dam, [209.85.165.104] even though the owner had personally witnessed both the fertilization and the birth and hence knew for sure who the foal's parents were. DNA from the stallion's blood samples also showed no evidence of a Y chromosome.
    • by BobPaul (710574) *
      Your description sounded really "out there" so I did some looking. There's a paragraph on wikipedia that gives a good summary: Chimerism [wikipedia.org]. The rest of the page is about intersex (hermaphrodite).
      • by NIckGorton (974753) on Tuesday March 27, 2007 @11:22PM (#18511041)
        Intersex is not the same thing as a hermaphrodite. All hermaphrodites are intersex, but the vast majority of intersex people are not hermaphrodites. To be a human hermaphrodite, you have to have ovarian and testicular tissue in the same person. Most people who are intersex have only ovarian OR testicular tissue. Instead of having both types of gonads there is some problem with sexual development in the womb that results in a person with physical characteristics somewhere on the spectrum between the poles of male and female bodies. (Hence the newer term for intersex conditions: DSD or disorder of sex development.)

        More importantly, if you call a person who is intersex a hermaphrodite many will likely be quite unhappy with you. Its akin to calling a Native American an 'Indian' - not only generally disliked by the people you are labeling but also factually incorrect because of a misunderstanding of what the term means (or on what continent you are located.)

        Nick
        • Its akin to calling a Native American an 'Indian' - not only generally disliked by the people you are labeling but also factually incorrect because of a misunderstanding of what the term means (or on what continent you are located.)

          Not really. Most Indians call themselves Indian or whatever specific tribe they belong to. Indian is likely a result of Columbus referring to them as In Dios - I'm pretty sure India as a country didn't quite exist at the time, and it's not that hard to figure out whether you

        • by asninn (1071320)

          More importantly, if you call a person who is intersex a hermaphrodite many will likely be quite unhappy with you. Its akin to calling a Native American an 'Indian' - not only generally disliked by the people you are labeling but also factually incorrect because of a misunderstanding of what the term means (or on what continent you are located.)

          That's not necessarily true insofar as that some intersexual people (whether they're true hermaphrodites or not) actually use the term "hermaphrodite" as a lab

    • Re: (Score:3, Interesting)

      by boingo82 (932244)
      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

    • by aebrain (184502)

      Unfortunately there's still so little research done on the more outrageously rare (we think) Intersex conditions, often because of sheer emberressment. Think how terrible it must be to be a self-fertilising hermaphrodite. Or to be a really spectacularly gorgeous-looking girl, who at age 17 or so finds out she is actually genetically male but with Complete Androgen Insensitivity (hence 100% female-looking rather than the 90-something most women are).

      Or worse, those women born with 5-alpha-reductase-deficien

  • DUP!! (Score:5, Funny)

    by dustball23 (309393) on Tuesday March 27, 2007 @08:10PM (#18509739)
    This story was already posted!! Oh, no, wait...
  • by The-Bus (138060) on Tuesday March 27, 2007 @08:13PM (#18509767)
    I understand it's mythologically correct to use the term "chimera" but whenever I hear it I always envision something else: a ghastly soulless beast with an iron heart, breathing fire out of a cavernous tooth-lined maw, crushing entire houses under gigantic feathered elephant legs; a scaled, whiplike tail kicks up ashy dust clouds as its dragged for miles behind this monstrocity.

    No matter how many times I hear the biological equivalent of the term (which is never as exciting) I'm always let down. I always think some giant monster has been discovered, or someone turned into this monster, or geneticists have new clues as to the cause of this monster.

    It's a bit annoying once I'm letdown but for a precious few seconds I'm always aghast in wonder.
    • I'm with you.

      One of these days, something from the Monster Manual is going to happen.

      I don't know if that's good or not.

      While it would be cool to see a Mind Flayer wandering about, it's probably not a good start to the day if you run into him.
    • I always envision something else: a ghastly soulless beast with an iron heart, breathing fire out of a cavernous tooth-lined maw, crushing entire houses under gigantic feathered elephant legs

      I see you've met my wife, then.

  • Serious question (Score:3, Insightful)

    by Anonymous Coward on Tuesday March 27, 2007 @08:16PM (#18509781)
    How is this interesting? What are the implications?

    (I'm sure it is, it just seems.. moot to me).
    • by khallow (566160)
      I see several things. First, it's another indication of the extraordinary stability of the reproduction process and is yet another route for evolutionary speciation (by shuffling around the chromosomes both in location and number). And it's an incredibly rare event. First, identical twins occur in 3 of 1000 births. Second, fertilization by two sperm (as occured here) is a 1% event. Assuming that they are independent of each other in frequency, then you have a 3 in 100,000 births event that probably is almos
    • 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.

      http://science.slashdot.org/comments.pl?sid=130374 &cid=10879347 [slashdot.org]

      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.

    • Re:Serious question (Score:5, Informative)

      by reverseengineer (580922) on Tuesday March 27, 2007 @09:03PM (#18510185)
      Well, this case is primarily interesting in the sense of "this thing that very rarely happens, it just happened." The main scientific benefit is that further light is shed on the mechanisms of human reproduction. Obviously, the outlines of that process are well-known, but there's still a lot of uncharted territory when it comes to the non-normal functioning on this process. Reproductive biology is an area where animal models (even in other primates) tend to translate rather poorly to human beings, and is of course also an area with ethical limits on human experimentation. Conceivably, learning about cases like this can advance knowledge about things like infertility and birth defects.

      There's actually an interesting story, almost the flip side of this rare case in humans, running now in the New York Times about marmosets [nytimes.com], in which a form of chimerism is quite widespread:

      One of the most surprising results of the study is that over half of male marmosets have chimeric sperm. Dr. Ross and her colleagues discovered cases in which the DNA of male marmosets turned up in babies supposedly fathered by their fraternal twins. In other words, the sperm came from one male, but it had the DNA of the male's brother. A paternity test would show that the baby's genetic father was actually its uncle. The scientists were not able to isolate DNA from marmoset eggs, but they did find that 2 out of 21 marmoset ovaries were chimeric. It's possible that a female marmoset can give birth to nephews and nieces.
    • What are the implications?

      Well, for the hermaphrodite twin, the implications are "corrective" gential surgury, followed by lifelong hormone therapy. Whether this is needed or even works at all is largely a secondary issue. You should read up about the expieriences of people born with ambiguous genitalia and the sufferring they have to endure at the hands of modern medicine and psychiatry.
  • by Anonymous Coward
    Well that should cock up the old joke about the blonde who gave birth to twins and wanted to know who the father of the other one was.
  • 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.
    • Furthermore, they really looked the part, being much closer in appearance than fraternal twins, but being subtley different from identical twins.
      The Olsen Twins?
    • by jd (1658)
      It should be possible to determine, provided the genetic material shared is not 100%. What will matter is how the genetic material is distributed. For example, in the story being described, the twins both have two sets of DNA. The presence of some gene G in both twins tells us relatively little. The presence of some gene G in the same subset of DNA on both twins would tell you much more, as would it occurring on one subset of DNA on one twin but in both subsets of DNA on the other.

      I'm not so sure about "p

    • Re: (Score:2, Interesting)

      by DavidTC (10147)

      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 gen

  • There's a great book series by Bryce Courtenay where the first book's (The Potato Factory) last story arc tells about the birth and childhood of a unique pair of semi-identical twins. The mother was a white woman who gave both a black man and an American Indian the right to have sex with her on the same night (long story, read it if you're interested) and had a pair of twins where one was black and the other white. The next book (Tommo and Hawk) was all about the boys and their teenage years living in Aus
  • ...welcome our freaks-of-nature-semi-identical twin overlords?
  • by wile_e_wonka (934864) on Tuesday March 27, 2007 @09:05PM (#18510207)
    I thought I would note why this doesn't happen all the time in humans (in some mammals it is common for an egg to be able to be penetrated by more than one sperm).

    According to my anatomy textbook, after the spem digests its way through the zona pellucida:

    The plasma membranes of the sperm and oocyte then fuse, and the sperm nucleus is engulfed by the oocyte's cytoplasm. This fusion induces the cortical reaction, wherin granules in the oocyte secrete enzymes into the extracellular space beneath the zona pellucida. These enzymes destroy the sperm receptors on the zona pellucida, preventing any other sperm from binding to and entering the egg.

  • The NY times reports today http://www.nytimes.com/2007/03/27/science/27marm.h tml [nytimes.com] the marmoset family of monkeys does this.
  • Well that explains a lot.
  • 023AD01('Semi-Identical', 'Twin')
  • Not to hijack the story, but:

    This story poses an interesting challenge for those people blocking stem cell research on religious grounds.

    The concept of the soul entering the zygote at the moment of conception raises puzzling questions when the resulting cell goes on to split into two viable individuals. What happens to the soul? Is it split in two? Does another soul enter the second? What happens when the individuals are not identical, do we get another soul?

    The situation becomes even more unte
  • It should be twin chimeras found. A cloned chimera is exponentially unlikely to be identical.

    Basically each chimera has two sets of semi-identical DNA. The identical portions inherited from the mother make it possible for the DNA to be identical enough to interface and mix together to create a single entity. The TWO stains of DNA are 3/4 average identical. But for the DNA to be compatible enough that the child is viable is rare.

    It's possible to have two children 3/4 identical just by chance. You would
  • Isn't that term used to describe *animals* which have cells originated from different zygotes?

    Or, it could be that the parents are named Typhon and Echidna.

    In a slightly related note: we've seen on slashdot FA about mouse with human braintissue, recently sheep with 15% human DNA in it, etc. I'm curious how far one will go in this, and where to draw the line. I can accept most human-like organs grown in animals for the benefit of medical advancement (e.g.replacing ones' organs without the current difficultie
    • When I say "severely restricted, if not forbidden outright", I mean in regard to treating them as animals.

      I had to think about the SF-book 'startide rising' where dolphins and apes are genetically altered to be as intelligent as us. If we ever create a chimera individual (or a race) with an intelligence comming close to our own (note: how to evaluate that, though?) they should have the same rights as ordinary people.

      The problem is, you will always have a grey area.

      Then again, I already think expirements on
  • Chimeras are possibly the limiting factor in DNA testing reliability. Chimeras include absorbed twin, maternal cells, sperm mitochrondial surviving fertilization. There is a short time window in the early embryo when this can occur.
    I remember seeing a case on Dateline TV where a child was removed from a mother because the standard DNA test did not match, even though the immediate footprint taken at birth did match. Turned out to be a rare case of father's mitochrondia. Same issue with the identificati

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