8. Genetic Variation

 It is said that selection is often assumed to eliminate genetic variation. The question is asked, why is genetic variation then not eroded over time? Genetic variation is a measure of the variation that exists in the genetic makeup of individuals withing a population. We know genetic variation still displays in organisms because of the diversity in phenotypes. It is an important force in evolution and allows selection to increase or decrease allele frequency. Throughout the year, we have seen many diverse mechanisms that can explain why genetic variation is maintained in populations, instead of being eroded overtime from selection. Mutations are constantly appearing due to many factors in our everyday lives. Selection does aim to get rid of these mutations, they still arise through environmental factors, DNA replication, and so much more. As we learned in class this year, some mutations can occur in an organism that could potentially be beneficial for fitness, and eventually the mutated allele would arise in higher frequency in the population. Then, another mutation could appear and switch the equilibrium. This brings us to the topic of mutation-selection balance, where it proposes how deleterious mutations are now a balancing selection. Another process we see that emphasizes genetic variation is genetic drift and gene flow. This is a process in which evolution of an allele frequency in a population change over generations due to chance (Khan academy). This brings about a variety of different genotypes and phenotypes. A certain example for this would-be reproduction of offspring through one kind of rabbit from a specific environment, mating with another species of rabbit from another different environment. With this, there will be rabbits in different areas, experiencing different alleles and traits, all due from genetic drift and gene flow.  Lastly, frequent dependent selection also maintains variation. This is when it prevents one allele from becoming to fixed in a population, so it will maintain variation.  We have learned that when one allele becomes frequent in a population, it will then be selected against so that the other allele will take rise. In this week’s lectures, we learned that genetic variation will not be eroded from selection, all with the help of many different mechanisms that explain the variation in populations. Variation is very important for evolution and keeps organisms able to adapt to the ever-changing environment. 

 

https://www.khanacademy.org/science/ap-biology/natural-selection/population-genetics/a/genetic-drift-founder-bottleneck