Blog Post Module 8
First of all, in order to understand how genetic variation is maintained in a population, one must first identify why genetic variation is important to have in a population. Genetic diversity essentially maintains the health of a population because it includes alleles that may be valuable in resisting diseases, pests, and other stresses. Maintaining diversity provides the population with a buffer against change, ensuring the flexibility to adapt. If the environment changes, a population that has different alleles will be better able to evolve and adapt to the new environment. In extreme situations (e.g. drought, disease epidemics) diversity could even mean resisting extinction.
Now, it is appropriate to discuss why genetic variation is maintained in the population. As seen in previous R exercises, mutations may arise in a population that could lead to further genetic diversity. Mutations such as double-stranded breaks, point mutations, and DNA polymerase mutations can all potentially disrupt the DNA sequence and lead to phenotypic differences. Next, migration into or out of the population leads to genetic variation. Individuals migrating into a new population could lead to more genetic variation because they may have different alleles. Mating of the new individual with individuals already in the population may lead to the presentation of new phenotypes in the population, thus maintaining genetic variation. In addition, the fitness and frequencies of certain alleles play a role in genetic variation. For example, if multiple alleles have the same fitness and frequency, they will be seen in equal amounts in the population, enhancing genetic diversity. Moreover, genetic drift describes random fluctuations in the numbers of gene variants in a population. Genetic drift takes place when the occurrence of variant forms of a gene, called alleles, increases and decreases by chance over time. These variations in the presence of alleles are measured as changes in allele frequencies. A population of kangaroos can have long legs and short legs with short legs being the dominant allele. By random chance, the offspring may all be short legs and this could reduce or eliminate the allele for long legs. These kangaroos may eventually evolve into a new species that can only mate and reproduce with each other, introducing entirely new genes into the population. In this way, Genetic drift can also cause a new population to be genetically distinct from its original population, which has led to the hypothesis that genetic drift plays a role in the evolution of new species. The last thing I want to talk is perhaps the aspect of genetic variation that I found most interesting. It is called negative frequency dependent selection and it occurs when the fitness of a phenotype or genotype decreases as it becomes more common. This, in turn, will ensure that no one allele in a population becomes the lone survivor in the population and maintains genetic variation in a population.
Works Cited
- http://maize.teacherfriendlyguide.org/index.php/genetic-diversity-and-evolution
- https://www.nature.com/scitable/definition/genetic-drift-201/
- https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/19%3A_The_Evolution_of_Populations/19.3%3A_Adaptive_Evolution/19.3C%3A_Frequency-Dependent_Selection
Hello Casey,
ReplyDeleteAs always, I enjoyed reading your blog and its interesting how we had many of the same points! I think we definitely approached the question in a similar manner. I love your examples you threw in, I think that was an excellent way to explain what was going on. The kangaroo example allowed one to see what was being discussed and show how traits can enter or leave a population. It's interesting how there are desired traits all around us yet we always seem to create new ones, and that's why genetic variation is so successful I suppose. There is always room for change and evolution will ensure that there is change.
ReplyDeleteHi Casey,
I really like how you labeled variation as a buffer against change for a population because it seems to be very helpful in making an adaptive change or response to selection much more manageable if it does not effect the entire population in the same way. The Kangaroo example is a great way of explaining why the diversity of alleles is so vital as a buffer as well. You mention negative frequency dependent selection which I found to be really interesting in the R exercise do you think that is a main driver of variation?
I love your input here! I think it is great that you tied your understanding back to the R exercises we have been doing in class. I can tell you have been learning and applying what we have learned in class to other aspects of your life!
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