Shenk supports his claims with an excerpt from a paper by Paolo
Vineis that discusses mutant and wild type strains, saying, "mutations
cause a change in what is called the 'norm of reaction,' that is, the ability of the organism to react to different environmental conditions" (194). A
disease caused by a mutation then cannot be treated the same in all
environments. How does this affect the nature vs. nurture paradigm and
support the GxE paradigm? If a mutant strain's reaction cannot be
predicted in an environment, how does this affect disease treatment and
control? What should treatment be based off of once the mutation is
detected?
Jenna Sherman (jsherm013@aol.com)
In general, the GxE paradigm completely obliterates the false dichotomy of the nature versus nurture paradigm. Under the nature versus nurture paradigm, mutations would simply not be considered, unless they were innate. In general, “nature” as being thought of in terms of being “the inheritance patterns determining genotypes in a manner often more complex than predicted by simple Mendelian genetics” (Campbell, 271), would only consider those mutations of DNA and RNA caused before a person is born, when mitosis and meiosis are taking place to create the cells of a human being, never considering the fact that the environment the person lives in could technically mutate the DNA they have, and rather its “norm of reaction” and how it is expressed, activated, inhibited, etc. Mutations occur within genetic material when there are “alterations of chromosome structure” (called trisomy, disomy, etc depending on the type of aneuploidy), “duplications of entire chromosome set” or even “divergence of gene-sized regions of DNA” (Campbell, 438-439) (http://en.wikipedia.org/wiki/Aneuploidy) Over time, these mutations are passed on through sexual reproduction, etc, and even more mutations can occur, or the now genetically modified DNA and RNA can stay relatively constant and be passed on, creating change over evolutionary time. Because the DNA and RNA have been modified in their function as a result of the mutation, the way they have a “norm of reaction” and “direct the production of proteins” will likely be different than their “normal” gene counterparts.
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However, even if an organism supposedly has the exact same mutation within its genes as another identical organism, if placed in different environments, then the organisms “wild types and mutants will differ in the norm of reaction” (Shenk, 194). The nature versus nurture would dictate that, if the behavior of an organism was based off nature, then all organisms with the same mutation should behave the same exact way, and on the opposing viewpoint, those who believe in nurture would say that two organisms which are genetically similar enough (even if one has a small mutation) would behave exactly the same way if gestated and grown in the same environmental conditions. However, the GxE paradigm proposed by Shenk, nullifies this theory, because it is obvious that organisms with the mutation and without the mutation, even if raised under the same “normal” conditions, show different “norms of reaction” to different temperatures, etc (Shenk, 194). An example of this would be an experiment done with Arabidopsis mutant plants, where the RD29A promoter was mutated under lab conditions. The plants were placed under different osmotic pressures, different amounts of light, and also differing temperatures. Although they had exactly the same mutation done in the same lab with the same environmental conditions, when allowed to grow, they had completely different results in the different environmental conditions in terms of amount of oxygen produced and photosynthesis that had occurred (statistically significant p-value of 0.003) (http://www.plantphysiol.org/content/119/1/205.full). Although a mutant strain’s reaction cannot be predicted in an environment, all that can be done is the testing of mutant strains in different environments until more is known, because in reality each will react differently due to the GxE paradigm.
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