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If identical twins have the same genes

  1. Mar 29, 2003 #1
    I just wanna ask a few questions on genes n hear some of your views...
    1)if identical twins have the same genes then how come identitcal twins still exhibit phenotype differences?( like one have a mole and the othe not having one)is it because of alles?
    2)Why is it that species cannot mate outside of their own species.ie,monkey and elephant.
    3)lastly, does eating cooked food really help developed the human brain into its 'intelligent' form today because of its high protein, and hence played a major role in man's evoluntionary path?
    Last edited by a moderator: Feb 4, 2013
  2. jcsd
  3. Mar 30, 2003 #2
    Re: twins

    i read that article and couldn't help think that realising how to cook food would be more a consequence of higher intelligence then a cause, that would explain the apparent correspondance of these events. i don't know it just seemed a bit improbable...
  4. Mar 30, 2003 #3

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    Re: twins

    Identical genes means that they will develop identically in an identical environment. Any differences between twins would be explained by environmental influences. For a Mole for example, would be due to sun damage.

    There is a whole range of potential environmental factor that could cause slight differences, and while I am completely unable to think of any of them (other than sun causing freckles differently etc) i can assure you that it is these environmental factors alone that cause differences between twins.

    It is easy to think of the answer to this question like this: DNA is a recipe. If you get a recipe for chocolate chip cookies, then you can make a chocolate chip cookie. If you have the recipe for a black forest cake, then you can make a black forest cake. But if you get the recipe of CCC and BFC, and follow both recipes in the one bowl... You end up with a mess.

    Nature, trying to follow the recipe, quickly aborts before the mess stage.
  5. Mar 30, 2003 #4


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    Re: twins

    What about gene regulation? I remember reading that gene regulation would created differents phenotype in identical twins. They didn't explain if the gene regulation difference was linked to environmentental factors.

    I also read that in female identical twins the X chromosome had to do with some phenotypic difference. The twins would not have the same X chromosome condensated. I don't remember how they call the condensated X chromosome.

    By definition, donkey and horse are still incompatible because the mule is infertile. As far as I remember, most of the incompatible is due the the number of chromosome. For example (don't known if the numbers are accurate)a horse has 48 (24 pairs) chromosomes and a donkey has 46 (23 pairs)chromosomes. The donkey is missing a pair, so the mule ends up with 47 chromosomes (23 pairs + 1 chromosome). The examples given by Sensei show species that are in the same genus. Being in the same genus make species less incompatible.

    I don't remember the other factor that are involved in the species barrier. Also keep in mind that there is sub-species which makes thing a more complicated. For example african bees can mate with european bees and have fertile offspring. Same species but 2 different sub-species.
  6. Mar 30, 2003 #5


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    Re: twins

    Eating cooked food could not possibly cause evolution due to its protein, as you are asking.

    The eating of the food comes after the genetic blueprint for the next generation has been fixed. For instance, if a woman eats cooked food with protein, it does not affect the eggs she has been carrying since birth. Clearly, an action (cause) which comes after the result (effect) cannot be useful as hypothesis. This is a common misconception about the relationship between behavior and genetics.

    Always remember, for any possible relationship to be meaningful, it cannot be a spurious correlation. It is a spurious correlation if there is no independent variable. There is no independent variable if there is no cause-effect mechanism at play. And lastly, the causal mechanism is supposed to be identified first.
  7. Mar 30, 2003 #6
    1)wat about identical twins with different thumbprints? no environmental factor can be taken into account here cos the baby alredy have different thumbprints when they out of the mothers womb.
    2)Does that mean that as long as 2 species whose number of chromosomes are almost silmilar ie, 46 and 48 they can mate but will hence produce infertile off spring?
    3) ermz lastly, i tink maybe the eating of cooked food allow for faster digestion relative to raw food alllowing for more time to do other things together with the protein intake may have been wat spur the development of the human brain.wat do u think?
  8. Mar 30, 2003 #7


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    I used the number to explain why the mule was infertile but I migth of been wrong. Got this from this web site http://www.madsci.org/posts/archives/may2001/989331026.Ev.r.html

    As far as I understand it, 2 different species can reproduce if they belong to the same genus. For example (it might sound sick) a human
    has 46 chromosome and the chimp has 48 but I don't think a chimp man would emerge due to the fact that human and chimp do not belong to the same genus. The question to ask is whether or not an Homo sapian and an Homo erectus could have offspring since they belong the Homo genus.
    Behavior could also explain why 2 species do not interbreed.
  9. Mar 30, 2003 #8
    yes it can. the womb is an enviroment. two babies in the same womb could have varied experiences. couldn't they?

    I have no idea if this would affect thumbprints
  10. Mar 31, 2003 #9
    I'm only guessing, but I imagine that when it comes down to fine details, dna probably doesn't worry too much. Especially bits that aren't really necesarry for a healthy existance. I think dna is a lossy algorithm to use an analogy. Things like fingerprints might have some vague encoding which extrapolates out in some chaotic manner while other more complex parts might hold more definite or detailed instructions.

    Raavin [?]
  11. Apr 2, 2003 #10
    but even in the womb they would share the same environment.shouldnt they?
    so why cant organisms mate outside their own genus? does is all attribute to behaviour?
  12. Apr 3, 2003 #11
    Similar but not completely identical. One twin might be pushed over to the side while the the other's hanging out upside down. Little differences can have large consequences after growing for nine months from a single cell to an eight pound fetus.

    Why can't you mate outside the genus? In eukaryotes there are two sets of chromosomes, to make a long story short, the extra copy is for redundancy, it helps correct mistakes in the complementary chromosome. If two species had drastically different chromosomes, or if one chromosome is missing (as in the case of several human birth defects) than the offspring would be born with severe problems. There are all sorts of molecular mechanisms to make sure that doesn't happen. I wouldn't be surprised if a sperm from one genus could enter the egg of another, but it wouldn't be viable. Anything close would be aborted. It happens in same species. I think the majority of human eggs fertilized by human sperm self abort rather than gestate, because of the number of errors.
  13. Apr 9, 2003 #12
    Re: Re: twins

  14. Apr 9, 2003 #13
    One thing that I think everyone should keep in mind when thinking about species and mating questions, is the FACT that species are defined by fairly arbitrary lines, the same with Genus. Just because something is called Homo sapiens, and another thing called Homo erectus, doesn't give you one iota of genetic information. There are some people who don't believe in any line of Homo except for Homo sapiens...
  15. Apr 10, 2003 #14
    Good point, i am actually one of those people.
    It is right that species and genus were not originally made depending on DNA, but DNA does come somewhere in the middle, eventually all mamifairs (not sure of the word) are all brought the same, they are a single cell, then the cell starts to become 2, then 4 ... etc.
    I can't see anything that will determine if this mamifair cell is a Human's or a Donkey's other than the number of chromosomes, and the genes.

    Anyway, i am not even sure of that.
    Stuff like moles, and fingerprints are not genetically driven.
    It is possible to get two identical twins, but one is born with a missing limb, and the other is perfect (ok, it is very rare !).
    So how about a very delicate thing like fingerprints, it will be very affected by the enviroment (inside the mother's womb), maybe the pose of the baby while the mother is walking will affect the fingerprints of the babies (you know, fluids will take different pathes round the babies, and fingerprints are very delicate).
    Maybe i am exagerating, but i am trying to let my point reach everyone :smile:.

    Eventually, i am no expert.
  16. Apr 10, 2003 #15
    why don't you believe in any line of Homo before Homo sapiens? I think the major collective fault of modern Homo sapiens is supreme arrogance. I am actually not trying to attack your point of view, but I am extremely wary as to scientific reasons supporting this viewpoint. I would be grateful if you explained, just so I could gain a better grasp upon views like these. Thanks!
  17. Apr 11, 2003 #16
    Well frankly, for me this comes more like a belief in religion then a scientifical beleif.
    But, if i like to ask (from a scientifical point of view this time), do we have any clue of having any specy under Homo other than Homo Sapiens ?
  18. Apr 11, 2003 #17

    Identical twins do have different fingerprints. Traits are affected by our genes as well as the environment. The DNA formed our fingers a certain way, and then the amniotic fluid in our mothers made tiny wave marks in our fingers and toes. If you take a pencil and rub it across a 3 X 5 card several times till you have a dark blob of graphite, then rub the bottom of your finger across it, you can take your blackened finger and roll it across a piece of white paper to see your fingerprint. A piece of tape helps to keep it from rubbing off, and a magnifying lens helps you to see it. Every one of your fingers will be different.
  19. Apr 14, 2003 #18

    I am afraid I don't understand the question you are asking...
    I believe you asked if there were any species (specy?) catagorized under Homo other than Homo sapiens...
    Well, as you know, there are human ancestors, such as Homo erectus and Homo habilis that are classified under Homo, and of course, Homo neandertalensis, aka Neandertals. SOME scientists call Neandertals Homo sapien neandertalensis and call modern human beings Homo sapien sapiens. I would go for the former nomenclature.

    Thanks for answering my question, and for not getting offended!
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