Tuesday, March 20, 2012
Argument - Epigenetics and evolution
It has long been understood that the genes you are born with are the same ones that you pass on. There was the idea that even though gene expression maybe different as a result of the environment, the genes that an individual posses remain constant. David Shenk challenges this idea. He says "Epigenetics introduces the concept of free will into our idea of genetics" (160). "Now we realize that everything we do...can affect our gene expression and that of future generations."(160) says Randy Jirtle, Director of Epigenetics and Imprinting at Duke University. How does the idea of epigenetics affect our view of evolution? Is it possible that this "free will" will give humans the ability to control genetic expression for themselves and their offspring? Will further research of epigenetics lead to the reduction of natural selection and an increase in the control of genetic engineering?
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First off, epigenetics is “the study of changes in gene activity that do not involve alterations to the genetic code but still get passed down to at least one successive generation” (http://www.time.com/time/magazine/article/0,9171,1952313,00.html). So in terms of an evolutionary whole, in my opinion epiginetics will not change our view of evolution as much as add to it. Never before was it thought that “environmental factors like diet, stress and prenatal nutrition can make an imprint on genes that is passed from one generation to the next” (http://www.time.com/time/magazine/article/0,9171,1952313,00.html), which is why our view of evolution will gain additions. To understand why our view of evolution will remain for the most part stagnant, one must first understand what evolution is. In reality, “Evolution is a process that results in heritable changes in a population spread over many generations” (http://www.talkorigins.org/faqs/evolution-definition.html). Many factors go into changing an organism’s evolutionary make up. Over time “a change in the nucleotide sequence of a gene may affect its function wherever the gene is expressed. In contrast, changes in the regulation of gene expression can be limited to a single cell type (Campbell 527). Currently, we hold the view that evolution is “a process in which new forms arise by the slight modification of existing forms” (Campbell 529). Essentially evolution is not goal oriented, but instead happens because it needs to happen over time for an organism to survive. An “evolutionary trend does not imply that there is some intrinsic drive toward a particular phenotype” (Campbell 531). Instead, evolution is a result of the interactions between organisms and their environment. Furthermore, if “environmental conditions change, an evolutionary trend may cease or even reverse itself” (Campbell 531). This, our current view, is in line with what epigenetics is. The only difference between the two is that epigenetics proposes that these evolutionary changes, or similar changes, can take place over the course of a few generations instead of thousands of years. Recent research also supports such a notion as well. It was recently found that Darwin’s theory deserve more credit than they have been getting. Prions, found inside cells can change shape based on environmental conditions such as temperature or the presence of chemicals. After they change shape, these proteins can collide with other prions and cause them to change shape as well. Soon after, “When the cell divides, both daughter cells will contain prions of both states, and the chain reaction can keep occurring in that new generation” (http://newswatch.nationalgeographic.com/2010/11/11/how_evolution_is_evolving/). When the prions interact with the rest of the cell, including the DNA, the different shapes of the prions can cause different proteins to be made, or different parts of the DNA to be read which triggers different phenotypes. So essentially, “some [prions] may actually become incorporated into the DNA” (http://newswatch.nationalgeographic.com/2010/11/11/how_evolution_is_evolving/) as a result of changes in diet, exercise, or lifestyle.
ReplyDeleteThese changes will then be passed down to the next generation. Taking all this into account, our view of evolution is only altered slightly in that it is now known that “life and evolution are dynamic processes, based on the complex back-and-forth relationships between organisms and their entire environment” (http://newswatch.nationalgeographic.com/2010/11/11/how_evolution_is_evolving/). This new, unprecedented discovery raises the question as to whether or not humans can control their genetic expression for themselves or even genetically engineer their offspring. Essentially, taking into account epigenetics and the standards that it is based on, humans cannot fine-tune their phenotypes. However, humans, hypothetically, can alter ever so slightly the way that their genes are expressed. In theory, if a person alters his or her exercise schedule, or diet over a period of time, then this will cause different genes to be expressed. As Shenk states “when individuals deliberately push themselves beyond the zone of relative comfort… they [induce] an abnormal state for cells in some physiological systems…[which] trigger the activation [of] dormant genes within the cells DNA” (69). Based off, this a person could expect to see minimal changes in their gene expression, if not that of their children; however, for significant changes to be made, it would take much longer to surface. All in all, I do not believe that further research in epigenetics will lead to the reduction of natural selection. Natural selection is “a process in which individuals with certain inherited traits leave more offspring than individuals with other traits” (Campbell 456). While it may appear logical that thos who manipulate their offspring’s phenotype through epigenetics would have increase chances of survival, it is important to note that epigenetics, although a new concept, has been occurring throughout the history of the world. Epigenetics is a part of evolution that is just become apparent to humans. So essentially, evolutionary history will continue as it has been because this is not a new occurrence, merely a new concept. Genetic engineering is a separate field, in which the genes themselves are manipulated in a lab setting, whereas epigenetics is gene manipulation through environmental stimuli.
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