Blog Post Module 8: Reflection Prompt


Selection is often assumed to eliminate genetic variation. So, why is genetic variation then not eroded over time? Based on what you have learned in the past modules, from the basic mechanisms of evolution to quantitative genetics, reflect on the diversity of mechanisms that can explain why genetic variation is maintained in populations.

- Based on what we've learned so far, genetic variation is maintained in populations because without genetic variation, a population would not be able to evolve to fit its changing environment. The presence of genetic variation implies that individuals of the population vary in the alleles they possess, meaning that individuals differ in genotype. Genetic variation allows natural selection to increase or decrease the frequency of alleles already in the population. Selection does not drive alleles to fixation. Phenotypic variation can either arise from genetic variation and/or environmental variation. Only the differences that arise from genetic variation can be passed on to future generations. Meaning, only a fraction of the genetic component of variation is actually heritable. Evolution can not occur if traits are not heritable. Genetic variation is advantageous to a population because it enables some individuals to adapt to the environment while maintaining the survival of the population. Mutations are the source of variation, but the process of mutation does not itself drive evolution. Mutation is a weak force in evolution because any mutation at any given locus is really rare.





Comments

  1. Victoria K.24 October 2021 at 15:04

    Putting it into genotype/phenotype is a great example! Just because a phenotype is being selected for doesn't mean that's the only way that phenotype will be expressed. To be super honest, I completely forgot about that when writing my post, so I'm glad you put it so succinctly!

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  2. Aaron 𓆟30 October 2021 at 18:41

    Not to piggyback off of Victoria's reply but I also like the breakdown between genotype and phenotype. It is an interesting take to say that a phenotype may be selected for but without a heritable genetic backing to that phenotype, the selection on such doesn't really matter so much. I suppose something could also be said about linked genes, genes that are expressed in multiple ways, etc- in that simple selection does not serve to squash the genetic variation arising from multiple different factors, other than just one allele combination at one locus coding for one specific phenotype which could then be selected against and wiped out.

    Also, pointing out that mutation really is a weak force is a such a good point. We want to place this insane importance on mutation as the origin of genetic variation while also failing to acknowledge that yes- mutation itself at a given locus is a rare event and surely the spread of that mutation through a population is even rarer.

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