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Thread: Is genetic deversity really essential?

  1. #1 Is genetic deversity really essential? 
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    Pulled up this article that examines the Iberian lynx discovering that they have had very little genetic diversity for nearly 50,000 years. It opens the question of important genetic diversity really is in keeping other maga fauna from extinction.

    Iberian Lynx Not "Doomed" By Genetics - Science News - redOrbit


    Can this be applied to other species, or is the Iberian lynx just special in some other way, such as particular resistant to diseases etc. The other surprise and a personal learning experience is I looked up maximum ice extent from the past couple minor ice ages and indeed tundra, which lynx don't typically inhabit, extends all the way to the Mediterranean sea and would have isolated the Iberian lynx from the rest of the European lynx to the East.


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  3. #2  
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    It apply to human too. I saw a National Geographic documentary that says human has a "genetic bottleneck" that reduce genetic diversity, which occured several thousand of years ago due to a massive volcanic explosion that destroyed alot of ecosystem and human too (occur near South East Asia). The documentary also said: this is where (~75,000 B.C) human learn to socialize and survive by being together while most other genetic variant desist (a.k.a we were 'domesticated').

    EDIT: something like this http://anthropology.net/2009/10/08/e...c-b-firstcite/ , but I saw the documentary, not this.

    And it also says that we are genetically less diverse than a monkey does with each other...


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    Genetic diversity is of course not necessary - any more than wide geographical spread, unspecialized diet or habitat requirements, and small to moderate size, are necessary.

    But that's the way to bet.
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  5. #4 Diversity Brings Survivability 
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    I read the article and i undestood what is the meaning of it. First i should say yes genetic diversity is mandatory to survivability of species becaust it gives population the power to resist changes in environment over long time .Each population has gene bank that consist of all posssible diversity in genes of individuals of that population.each generation shows a group of diffrent people , not all of them will survive but those who have better adoption with their environment.In fact it is the environment that cuases change in the number of dominant individuals in specific population(those who survive) and even the amount of diversity in specific population ,For instance consider contemporary horses ,they were small in first place and they were living in forest, their small body was giving them the benefit to adopt in environment consisted of trees and bushes were small body helped them to hide better from the predators.Their gene bank had characteristics like bigger body but they could not survive in forest because their body was ineffective from moving to finding food. suddenly environment changed(forest burned) so they came and were habitant of plains where for hiding from predators or finding food nothing was better than bigger body that gave them ability to run quickly in plains so those who were small died(killed over time) and even if they were borning, they could not survive (that specific characteristic is not useful for being survive in that environment),over time number of big horses grew but not small ones`s.now what would happen if horses population had not that kind of gene?whit chganges in environment they were extincted.less diversity in population most of the time is cuased by sudden change that kills massive number of one population so the small group that survives will form new population with less gene diversity compare to original one .Genes in this group after long times becomes so similar that even organs or tissues can be replaced between them.this is a point that population is over the edge , any change even small that is harmful for sirvivability of that speicies cuases them to be extincted.In The Iberian lynx`s population long time ago environment cuased massive decreasing of individual and now for long time their environment is persistant so they survived even with less diversity in genes(that is definitly won`t last long).it can happen to any population but it is cuased by environment.Under any circumstances diversity brings survivability.About the human genetic bottleneck i don`t know anything(I don`t think that is true) please if you may provide more information.
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    From my (very basic) understanding, genetic diversity is essential in a species survival in areas where the environment is susceptible to rapid change. Some species may inhabit areas that are not subject to much environmental change at all; in this case, a wide genetic variability is not particularly essential.
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  7. #6  
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    Good point. One thing that also contributes to natural selection in animals is the background population of pathogens in the environment. This is a very variable population that can rapidly evolve; in humans, there are some evidence to suggest that we are instinctively attracted to others who have significantly different major histocompatibility complexes (MHC; or human leukocyte antigen [HLA]; Major histocompatibility complex - Wikipedia, the free encyclopedia, section on MHC and sexual selection), the offspring of such people would have a greater diversity of MHC (the molecule that recognises self from non-self, i.e., recognises foreign substances and contributes to an immune response) and therefore could withstand a greater diversity of pathogens and would be more likely to live long enough to reproduce. Personally, I feel that physical attraction and personality contribute greater to the pairing of partners, and with the ever increasing standard of medical care worldwide, people who have relatively poor immune systems could live long enough to reproduce. Nevertheless, trials with MHC and sexual selection have also been done in mice using mazes and have significant results, suggesting that it could have a greater role in other animals.

    In the production of vaccines, one of the pre-requisites is that the vaccine is effective in diverse MHC backgrounds. A vaccine works by triggering an immune response and producing memory B and T cells that will be able to rapidly divide upon a subsequent recognition of the same antigen (on the wilde-type pathogen). A vaccine produced and tested in the USA may have positive results because the subjects have similar MHC and can recognise the vaccine, however, running the same trials in, for example, China, where the MHC allelles may be substantially different than that of the population in USA, may not yield the same positive results. The extent to which MHC in isolated populations can differ was shown when Europeans introduced smallpox and other diseases to the Native Americans, by some estimates, killing approximately 90% of the population.

    The requirement of genetic diversity is also highlighted in arable farming. If you select for a particular trait in a group of crops (such as yield) by breeding only the highest yield crops with the highest yield crops you produce a population that is very similar genetically, this can also coincide with a susceptibility to a particular pest/pathogen, and if one plant was to become infected, the disease would most likely spread rapidly throughout the population.
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    You obviously know a lot more about this subject than I do! I found your HLA statement really interesting and will definitely read up on that. Is there any particular reason why that may be so?
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    Here's the abstract of the paper reporting the famous T-shirt experiment by Wedekind in 1995: MHC-dependent mate preferences in humans. [Proc Biol Sci. 1995] - PubMed - NCBI. There's a view interesting points from it:

    "Here we show that the MHC influences both body odours and body odour preferences in humans, and that the women's preferences depend on their hormonal status."
    Potentially corresponding with reproductive cycles.

    "Female and male students were typed for their HLA-A, -B and -DR. Each male student wore a T-shirt for two consecutive nights. The next day, each female student was asked to rate the odours of six T-shirts. They scored male body odours as more pleasant when they differed from the men in their MHC than when they were more similar."

    The greater the difference, then the greater diversity of HLA the offspring will have, therefore it will be able to deal with a greater amount of different viruses and bacteria. In most cases, in order for an effective immune response to occur, the HLA, which is a embedded on the cell membrane of antigen-presenting cells, must present the antigen to the T cells, thereby activating them to attack the pathogen. Having different alleles to produce HLA from will ultimately increase the net effectiveness of antigen presentation. There's evidence that demonstrates a correlation between the richness of pathogens in the environment and the diversity of HLA within the population (here's a summary of one such paper). I also remember reading a study about Three-spined stickleback populations and their MHC (but had a bit of difficulty finding it on google...); the population was divided by individuals that preferred the river and individuals that preferred the lake. They analysed the lake and the river for parasite load and diversity, finding a greater load and diversity in the lake than the river, then they analysed the stickleback MHC and found that the lake fish had 18 MHC alleles, the river fish had 9, 8 of which were shared by the lake fish. Another study then placed males and females of the two groups in a tank of flowing water that was divided in the middle; females preferred spending time in a flow of water when there was a male upstream that was from the same habitat (either lake or river) as they were from. This suggested that the different parasite load and diversity in the two habitats was beginning to contribute to speciation as it was contributing to sexual choice in the fish, and, in the processes, increasing genetic diversity.

    Back to the Wedekind paper...
    "This difference in odour assessment was reversed when the women rating the odours were taking oral contraceptives."
    This was thought to be because oral contraceptives hormonally simulate pregnancy, but we can only speculate as to why pregnant women would rather not be around people with dissimilar HLA.

    "Furthermore, the odours of MHC-dissimilar men remind the test women more often of their own actual or former mates than do the odours of MHC-similar men. This suggests that the MHC or linked genes influence human mate choice today.
    "
    But the effect isn't quantifiable so it's difficult to say just how much it influences mate choice.
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    Excellent! Really cool stuff. Thank you very much.

    Now I'm curious. I wonder what my boyfriend's HLA is
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  11. #10  
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    "Each male student wore a T-shirt for two consecutive nights. The next day, each female student was asked to rate the odours of six T-shirts."

    Smell his T-shirt
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  12. #11  
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    Haha, I think I might do that!
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