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Thread: Is it always the case that a gene is either dom or reces?

  1. #1 Is it always the case that a gene is either dom or reces? 
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    Is it always the case that a gene is either dominant or recessive?

    I mean obviously it is generally so, but is it exclusively so? Are their times when the expression of a gen comes from both sides?


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  3. #2  
    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    A lot of alleles are co-dominant, so yes. Most of the time it isn't really as simple as dominant/recessive, especially when more than one gene is involved in producing a phenotype.


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  4. #3  
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    Merci bien,
    I thought something like this would be happening, nothing being simple as Yes or No.
    Is there some method of determining dominant viz recessiveness?

    My suspicion is that it will be a number of arbitrary features of the gene's expression that will determine this?
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    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    Essentially, a good way to think of how recessive alleles work is that they are often versions of a gene that produce non-functional/dysfunctional products, but in the presence of an allele that produces a functional product they don't have a significant effect on the phenotype. It's only when you have two copies of the non-functional allele that you get the recessive phenotype.

    http://en.wikipedia.org/wiki/Glutath...ase_deficiency

    Glutathione synthetase deficiency is an example of a recessive disorder that functions like that.
    "I almost went to bed
    without remembering
    the four white violets
    I put in the button-hole
    of your green sweater

    and how i kissed you then
    and you kissed me
    shy as though I'd
    never been your lover "
    - Leonard Cohen
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  6. #5  
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    Quote Originally Posted by i_feel_tiredsleepy
    A lot of alleles are co-dominant, so yes. Most of the time it isn't really as simple as dominant/recessive, especially when more than one gene is involved in producing a phenotype.
    I remember reading (I think it was in the Ancestors Tale) about how the genetic environment of a gene can greatly influence its expression.
    In a population of moths have industrial melanism the gene for this is dominant, creating two morphs (normal, or black). When a researcher cross bred them with another population of the same species (or perhaps a closely related species? It has been a few years since I have read the book) the same gene for industrial melanism instead could produce a large range of coloration in between, being codiminant rather than dominant in the presence of the different genes of the other moth. Both had the same normal coloration.
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