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Gender genes

  1. Feb 6, 2006 #1
    In a male, gender gene is expressed as XY, so people know how a male to be male by its Y, but in a female, the gene is XX, and I am wondering which one of XX is characterized for female... If the left one is, then what is the functionality of the right one ?
     
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  3. Feb 6, 2006 #2

    Monique

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    X and Y are chromosomes and on those chromosomes there are genes. There are less genes on the Y chromosome than on the X chromosome, females only have one X chromosome active in a cell (it could be either one).
     
  4. Feb 6, 2006 #3

    selfAdjoint

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    The Y causes a release of testosterone during a particular phase of embryonic development; this causes the male characteristics to develop. If the Y is not there this doesn't happen and "normal" development produces female characteristics. The two X chromosomes in the female don't actively make the embryo female. But they have other genes on them that are inherited normally with dominants and recessives. Either one could be on either X for different loci.
     
  5. Feb 6, 2006 #4

    matthyaouw

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    Possibly a bit of a silly question here, but what would happen if an egg cell were to be artificially given a Y chromosome instead of an X? When fertilised, would an embryo even develop with YY?
     
  6. Feb 6, 2006 #5

    iansmith

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    That would be impossible since the X chromosome carries vital genes for male developement, such as the androgen receptor (AR) gene, and other key genes.

    http://en.wikipedia.org/wiki/Androgen_insensitivity_syndrome
     
    Last edited: Feb 6, 2006
  7. Feb 8, 2006 #6
    Many people I have met usually think since X and Y are male's chromosomes and the presence of X in male creates a balance in men's femininity, anyone who can't control such a balance will become gay. Is that true ?
     
  8. Feb 8, 2006 #7

    Ouabache

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    Here's a little curve, I believe for honey bees, the males (drone) only have a single X, whereas the females (workers, queen) have XX .. Some food for thought (pardon the pun)..
     
  9. Feb 8, 2006 #8
    If it were curve, it couldn't be little,
    I have read a couple of articles on science mag about birds'Z and W chromosomes. How do people explain my question above ?
     
  10. Feb 9, 2006 #9

    Monique

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    Different organisms use different mechanisms to determine sex. Most nematodes also have a XX/XO system (hermaphrodites are XX, males are produced by meiotic disjunction that results in the loss of one X chromosome).

    Mammals have a dominant Y chromosome and silence the extra X chromosome in females and both Drosophila and C. elegans use the ratio of X over the autosomal chromosomes to determine the sex. More information about the evolution of sex determination can be found in this book chapter:

    http://www.wormbook.org/chapters/www_evolutionsexdetermin/evolutionsexdetermin.pdf
     
  11. Feb 9, 2006 #10

    Ouabache

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    Sorry I didn't have a chance to finish my above post..

    I believe for honey bees, the males (drone) only have a single X (no Y), whereas the females (workers, queen) have XX .. So the male honey bees actually have XO as Monique had described. Even more peculiar the male is not only missing the Y but also the rest of the second set of chromosomes. All male bees develop from unfertilzed eggs. They are therefore haploid (1N). The female bees (workers and queen) develop from fertilized eggs and are diploid (2N).

    Try some Mendelian genetics with that combination. In any given cross, we may wonder what is the probability of a particular genotype occuring in the queen. (assuming there is only one queen per hive).

    I don't know about the X chromosome creating a balance in man's femininity. There are males who exhibit very strong masculine traits (football players, boxers, weightlifters). They all carry an X chromosome, would you say that is balancing their femininity?

    Now I have also met a male who exhibited some effeminate behavior (vocalism, hand gestures), yet also was married, had 3 children and was a strong father figure. My guess is that his gene's dictated a different balance of hormones compared to the macho-males.

    I don't believe it is a matter of controlling a balance between a male's X & Y. Unless you really mean their hormonal balance. This balance appears to influence a wide spectrum in both females and males, from masculine to feminine behaviors.
     
    Last edited: Feb 9, 2006
  12. Feb 10, 2006 #11

    Monique

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    There are people with an XXY karyotype. I don't know the details of the clinical manifestation, but I don't think that the phenotype is fully penetrant. First signs will show up in males during puberty, you can google for more information.
     
  13. Feb 10, 2006 #12

    jim mcnamara

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    There are 'XXX' females as well. See Thompson & Thompson 'Medical Genetics' for the whole range of anomalies from Crie du Chat syndrome to the forms of anomalies described variously as Duschennes' Familial Idocy.

    Some genera of reef fish change gender 'on demand', as a response to the environment.

    The mainfestation of gender, even in mammals, is really complex
     
  14. Feb 10, 2006 #13

    Monique

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    There are also X females, they manifest themselves with Turner syndrome.

    An interesting (and sad) case is the boy who was raised as a boy after he lost his penis during a circumcision. He was castrated and received hormones to switch gender. He had an identical twin brother and was never told he was actually a boy until puberty when he himself came with the idea that he wanted to become male (in hindsight he had had a troublesome childhood due to the gender confusion, although I think the yearly psychiater meetings must have been a large influence). They are known as the John/Joan twin in the literature. The treating doctor believed that gender differences are not inborn, but are created by the environment.. which was shown wrong in this example.
     
  15. Feb 11, 2006 #14
    It's a choice as a social adaptation towards benefits for self, a sign of social behaviors' diversity, absolutely not a disease, whereas XXX is truly a genetic abnomality, sickness!
     
  16. Feb 11, 2006 #15

    Monique

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    Sorry, what are you saying?
     
  17. Feb 12, 2006 #16
    oh well, i guess he mis-wrote anomali to abnormality


    i think i understand it best
     
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