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How Likely For Trait to be Preserved Across Large Population?

  1. Jul 28, 2013 #1
    I'm trying to understand the impact of gene clustering on genetic inheritance, and to get an overall sense of what the state of knowledge is in this area (i.e., how much is currently unknown?)

    By way of example, say an original group of geographically isolated people we now call "Spanish" had "Trait X"--that is some phenotype based on a number of different genes or potentially some clustering of genes that spread across the entire population.

    Do we know with any certainty how likely it might be for "Trait X" to be preserved across all people who are related to original "Spanish" group (but who may have interbred with other historically geographically isolated populations?) For example, are there non-Mendelian mechanisms (currently known or potentially unknown) that might make preservation of the "Trait X" cluster more likely than other simple mendelian traits?

    Thanks, Jon
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  3. Jul 28, 2013 #2

    jim mcnamara

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    I'm not sure what you mean, but let's start with this:

    If 'Trait X' gives its bearers the ability to reproduce more successfully than the alternatives (call them 'Traits somethingElse') then 'Trait X' is more likely to propagate through the whole population than is 'Traits somethingElse'.

    I am not sure that is what you are asking.
  4. Jul 28, 2013 #3
    No, my question is once the trait spreads through the population (and assume the trait is not directly related to improved reproduction); then, after that, the population is no longer isolated, are there mechanisms which might maintain the trait to a higher degree than would normally expected...
  5. Jul 28, 2013 #4
    I'm not a biologist but I'd find any mechanism, that maintains a trait not directly related to improved reproduction at a higher degree than normal, very interesting, regardless of whether the population is isolated or not.

  6. Jul 28, 2013 #5
    You are basically asking if genes will diffuse into the larger population, correct? Your question is a funny one because you're asking something most people would never bother to ask once they've understood Mendelian genetics.

    I don't think this is the answer you are looking for: inbreeding, incest, Oedipal complex and whatnot can all preserve Trait-X. This is how animal breeders, such as fish and shrimp, breed unique forms of a species until it is no longer anything like the wild specimens. The same goes for plants and crops. Most common are the dog
  7. Jul 29, 2013 #6


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  8. Jul 29, 2013 #7


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    And genetic drift applies as well.
  9. Jul 29, 2013 #8
    Thanks, that's a constructive response.

    Now, once a set of genes become fixed in a population, could it be preserved once the population is no longer isolated, due to dynamics related to clustering, or how control genes (FKA "junk" DNA) interact with the Trait X genes?
  10. Jul 29, 2013 #9


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  11. Jul 30, 2013 #10


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    A way it can be preserved or increased in the population though not in itself having any selective advantage is when its locus genetically closely linked (close to) another gene with an alolele that is positively selected for. That is called linkage disequilibrium and can last centuries and millenia.

    Another thing sometimes seen is the small untyical population expands greatly due to historical or cultural factors. Perhaps not quite that but nearly is the high frequency of some alleles that are not common in the general European population whence they ioriginated, amongst Quebecqois or Afrikaans.
  12. Jul 30, 2013 #11

    jim mcnamara

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