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Do genes "fight" to get expressed?

  1. Jul 31, 2017 #1
    I am not sure if this is an epigenetic question or not, I am not too familiar with this field, so I hope it makes sense.

    Do genes ever “fight” to express themselves? I guess they do initially when time comes for it to be decided which one gets expressed? Is one gene "stronger"? Is there an electromagnetic force play happening of sorts?

    Also, throughout the organism’s life are there certain genes that would try to express themselves but the “defensive” system of the organism wouldn’t allow it? Therefore, only the “dominant” genes keep expressing themselves. Does anything like this happen in the organism? My guess to this one is no, but I'm not sure.

    I would really appreciate any feedback!
     
  2. jcsd
  3. Jul 31, 2017 #2

    BillTre

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    If I reinterpreted your question to something more like do genes compete for resources needed for expression, I would say not that I know of and in most cases no. I cold be wrong though.

    However, there are two situations where some genes get expressed but others don't.
    One would be in the female mammals. Female mammals have two x chromosomes and males have only one.
    Because there are twice many of each X chromosome gene in the females, there could be twice as much of production from them in the females. This would be "bad" in that there would be an "imbalance" of gene expression levels (relative to other genes not on the X chrromosome).

    The solution mammalian females have evolved is to completely inactivate one of the X chromosomes. This happens randomly early in development and forms Barr bodies. Which chromosome gets inactivated is can be different in each cell at the time of inactivation. The inactivation is then inherited in each cells progeny as development proceeds.
    Its not a fight, but a random choice.


    Another interesting case are male and female imprinted genes (also mammals). In this case genes from the mother or father are differentially imprinted (DNA or histone methylation) which prevents their expression in the offspring. The genes imprinted in the male are different from those imprinted in the female. The zygote resulting from the combination of the male and female gametes will therefor have a full complement of functional genes, some from the male and some from the female.
    For this reason, mammals derived from only the male or female genome are not viable.

    The hypothesized evolutionary reason for this is deal with competing interests of the male and female genomes. The male part of the genome will want to take advantage of the female to make the best offspring possible. The female genome will want to conserve her resources to better leave more offspring. Thus males genes that might make a super-big placenta which would make a single great offspring (or maybe a litter of them), but might use up all the females resources, leading to her early demise. Therefore genes that would do that get from the male get inactivated. This removes any selection those genes would feel that could select that effect.
    Again, not fighting but different genes being expressed different depending on which sex they spent the previous generation in.
     
  4. Aug 1, 2017 #3
    Thanks BillTre, those are really good examples. I am really trying to wrap my head around the general functioning of these systems.

    I guess a "fight" is more a metaphor that means the "dominant energetic state" of the organism? Even fights are in the name of "settling" disputes in order to arrive at some "better social equilibrium".
    Would it be fair to say even though many steps are random choozings, different biomolecules that emerge out of all this do carry an energetic field that is "stronger" or "has dominant energetic pull/influence" in the organism?

    Basically, the genes that build a red blood cell are the "winners" in the game of building a red blood cell, even though all the other genes are right there in the cell.

    I am trying to think of this in terms of "regulation". It has to happen. If that makes sense.

    Many thanks again!
     
  5. Aug 1, 2017 #4

    BillTre

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    I think of gene regulation as determining how the mechanisms controlling each gene are set, at the time in question, in a very mechanistic manner.
    Some of the choices involved in creating the situation could have random steps in them, but there is still some/many molecular mechanisms underlying the process and a history that the mechanisms went through to arrive at their current state. Some of those steps might have been competitive (as in fighting) in some way (such as how nerve endings might compete for a limited supply of nerve factor molecules required to maintain their large axon ending arbors), but they are still mechanistic and molecular in nature. This is also the approach I would use to explain why certain genes would be on in a particular cell type.

    If you want to say that some state has a greater influence on certain things, that seems OK.
    Using fighting as a stand in for competition at times also seems OK in some cases, as in: natural selection:: fight for survival.
    However, when I am being careful, I try to use a more mechanistic, non-anthropomorphic set of words to certain avoidable problems in understanding and focus on what I consider my real intended meaning.

    By the way, I think you ask really interesting questions.
     
  6. Aug 1, 2017 #5
    Thanks BillTre! That totally makes sense.
    And glad you find the questions interesting, in the last little while, I've taken myself down an interesting road of trying to understand all this stuff. Sometimes I almost wonder if I wander off too far.
     
  7. Aug 1, 2017 #6

    jim mcnamara

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    Biosynthesis/biodegradation is the expression of genes at work. There are examples of two biosynthetic pathways that begin with a common molecule where the final end products are two (or more) completely different molecules.

    Example, required by humans - the fatty acid docosohexanoic acid (DHA), found in some fish, some algae species and weakly synthesized otherwise:

    For humans that require synthesizing it, human synthesis of DHA, from alpha-linolenic acid (ex: ALA is found in plant oils: canola oil, flaxseed oil) is limited and therefore may be considered inefficient compared to needs. The molecule is important in modulating inflammation, and is a major component of neurons and the retina.

    The pathway is ALA -> eicosopentanoic acid (EPA) -> DHA The last step is the one that is inefficient. Estimates range near 15%.
    https://en.wikipedia.org/wiki/Docosahexaenoic_acid

    This whole process is why nutritionists suggest eating oily fish (tuna, salmon) and olive, canola and/or flaxseed oil in the diet of cardio patients (and people who do not want to be cardio patients). Pregnant and lactating mothers, too.
     
    Last edited: Aug 1, 2017
  8. Aug 1, 2017 #7
    Gene expression is controlled by the environment it finds itself in, a few thoughts; genes cannot do anything in isolation, they are part of a complex system. The exist an a nucleus with lots of other genes, some of which are responsible for controlling expression at certain times and at certain levels of intensity. The nucleus exists within a cell, the intracellular environment both generate and transmit chemical messengers to the nucleus, which influence gene expression. The cell exists within an organism which uses a vast array of chemical messengers which the cells and ultimately the genes respond to. I think the prevailing view is that genes carry out single specific functions, though this is being increasingly challenged. However if this is true, how would a gene “know” it had to compete and compete about what.? This would either require other genes which coded this information or control at a different level. It would be potentially damaging for genes to compete, in a complex organisms there actions must be co-ordinated.
    Of course this may not hold true for mitochondrial DNA which has a different evolutionary history and in humans only the maternal mtDNA is inherited any paternal mtDNA is destroyed.
     
  9. Aug 1, 2017 #8
    The combination of genes in sexual reproduction essentially is random.
    Sometimes a happy throw of the dice produces a phenotype which is extraordinarily successful.
     
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