Identical Twins and Homosexuality

Discussion in 'Biology & Genetics' started by Orleander, Dec 16, 2009.

  1. Orleander OH JOY!!!! Valued Senior Member

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    Since you are born gay, if you are gay does that mean your identical twin would be gay as well?
     
  2. Nasor Valued Senior Member

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    If one twin is gay, the other has about a 50% chance of being gay - so it's far from certain, but the odds are a lot higher than average. This seems to indicate that there's a substantial genetic component, but that genes aren't a single deciding factor.
     
  3. GeoffP Caput gerat lupinum Valued Senior Member

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    I was surprised how rare the penetrance was in the other identical sib. So on guess homosexuality is 50-70% environmental or residual variance. Strange. Then again, they're coding what could be expressed quantitatively as a binary, so maybe odd ratios aren't so unexpected.
     
  4. Orleander OH JOY!!!! Valued Senior Member

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    could it be because of something happening during the pregnancy and it not being genetic?
     
  5. Idle Mind What the hell, man? Valued Senior Member

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    Just because it happens during pregnancy, doesn't mean it's not genetic. Genes as well as environment dictate how an organism develops. There are genes that are only active during embryonic phases, for example.
     
  6. Hercules Rockefeller voltage gated ion channel Moderator

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    There is likely to be a genetic component to homosexuality. Scientific studies of homosexuality running in families agree with this. However, this does not mean that the trait is determined solely by genes. Like nearly every trait, there is almost certainly a mixture of nature and nurture (genes and environment) at play.

    So, when it comes to monozygotic twins, homosexuality is like other complex personality traits – they may or may not be shared with the chances being almost impossible to determine beforehand.


    Really? Who says this?
     
  7. Repo Man Valued Senior Member

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    http://www.bri.ucla.edu/bri_weekly/news_050812.asp

    Fraternal birth order's influence on homosexuality wasn't known at that time as far as I'm aware, so that may have altered the interpretation of these findings.
     
  8. S.A.M. uniquely dreadful Valued Senior Member

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    Hormonal changes in womb environment have been postulated as a factor. Perhaps a comparison between identical and fraternal twins may be useful.

    One cannot underestimate the psychological effects of twins on each other. People expect identical twins to be similar.
     
  9. Hercules Rockefeller voltage gated ion channel Moderator

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  10. Asguard Kiss my dark side Valued Senior Member

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    orleander, there is a 50% chance that if you are schizophrenic then your identical twin will be too which means there is a genetic componant there as well (i cant rember the full list of percentages but it was an interesting list) however it shows its not CERTAIN that you will be and that there are enviromental factors as well (hense its not 100%)
     
  11. Ahem embrace simplicity Registered Senior Member

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    No. My nephews are identical twins. Barry is gay. Brian is not.
     
  12. edenocp Registered Senior Member

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    In the study, none of the identical twins raised separately were both gay. Not 50%
     
  13. Grim_Reaper I Am Death Destroyer of Worlds Registered Senior Member

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    So 1 in 3 are born gay so that means if you have triplets one of them are gay?
     
  14. Idle Mind What the hell, man? Valued Senior Member

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    No, that's not a reasonable assumption.
     
  15. Nisus by peace he shall destroy many Registered Senior Member

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    yea if they are siamese twins.
     
  16. baftan ******* Valued Senior Member

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    This is clever...
     
  17. Orleander OH JOY!!!! Valued Senior Member

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    well, if its genetic, is it possible for one identical twin to have Down Syndrome and the other not?
     
  18. Idle Mind What the hell, man? Valued Senior Member

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    No, I don't think so. The genetic abnormality that causes Downs Syndrome is a trisomy of chromosome 21 -- three copies of the chromosome in each cell, instead of two. So in order for this to happen, it would have had to obtain the extra copy from one of the parent gametes. Fusion of the gametes to form the zygote happens prior to the zygote spliting into two during the first cell division, which is when identical twin formation occurs.

    I think.
     
  19. Bishadi Banned

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    a hemaphrodite is born gay.

    (more cleft palet births then them folks)


    all others learn it
     
  20. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    Really?
    So what sex, exactly, is a "hemaphrodite"?

    So what?
     

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