Epigenetics can control gene expression and is affected by our lifestyle choices. According to Randy Jirtle, “before, [we thought that] genes predetermined outcomes. Now [we realize that] everything we do– everything we eat or smoke– can affect our gene expression and that of future generations” (160). If what we do can affect future generations, then how will the vast availability of cheap unhealthy foods and the use of machines for convenience in our generation affect the gene expression of future generations? Use your knowledge of epigenetics to help answer the question.
Dylan Kuper ( dylan.kuper@gmail.com )
The basis of Epigenetics is the study of the "nongenetic cellular memory,which records developmental environmental cues(and alternative cell states in unicellular organisms)(http://www.sciencemag.org/content/330/6004/611.short)." This memory can often be as a result of histones, which not only package DNA but "serve as a mediator for gene expression, telling genes when to turn on and off p(159)." As Shenk explains the epigenome can be altered by the environment (p 159-p158). Also, as we learned in Chapter 18, changes in the epigenome can be passed on to future generations. Therefore, not only is the epigenome moulded by the environment but these changes to the epigenome are passed down from parent to offspring.
ReplyDeleteAn experiment conducted with mice determined the effect of a mother’s diet on her offspring’s epigenome. Two groups of mothers were used. One pair of mothers was fed a diet rich in methyl, while the other group was fed a diet which did not contain much methyl. The pups of the group whose mothers were fed methyl-poor diets had offspring that were the obese, yellow in colour, and at a higher risk to develop diabetes and cancer. This was because of the unmethylation of the agouti gene, which is present in both humans and mice. This gene was unmethylated in the mothers with the methyl-poor diets and therefore was unmethylated in the offspring. This experiment proves that the diet of parents has a large effect on the epigenome of the offspring. (http://learn.genetics.utah.edu/content/epigenetics/nutrition/)
Researchers at the Temple University in Philadelphia have gone further to associate methylation with a high fat diet. They have discovered that in patients with colon cancer, methylation patterns on a persons genes that are involved in the breakdown of fatty acids, carbohydrates, and proteins are being changed. These changes are also often caused to insulin genes that create more insulin than is required by the body. (http://www.alive.com/posts/view/307/how_fatty_foods_trigger_colon_cancer?cpage=1) From this experiment it is clear that the epigenome is effected by the diet. According to the Food and Agriculture Organization of the United Nations, Obesity is increasing around the world and one of the reasons is due to diets which are not rich in vitamins and minerals. As this trend continues it seems likely that not only will parents have unhealthier diets but due to the epigenome, so will children.
The epigenome can also be affected by physical activity, or lack thereof. Dr. Moshe Szyf, a researcher from McGill University, has said, “As for our modern lifestyles, exercise is good, but not just for burning calories. It may reprogram our genes (http://www.theglobeandmail.com/news/technology/science/code-2/article154530/page1/ ).” According the Dr. Szyf, physical activity could change the epigenome and cause the turning on or off of genes that in the past were helpful for long winters. In this case, it could be helpful for humans to have this gene turned of in order to store less fat in their body and arteries which could lead to arthrosclerosis and eventually arteriosclerosis. With the increased use of machinery in our daily life it seems as though we will be involved in less and less physical activity. This will not cause beneficial changes in our epigenome that we could have passed on to offspring.
According to Time Magazine, 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). It may seem as if epigenetics has now “accelerated evolution”, but one must understand that “evolution is a process that results in heritable changes in a population spread over many generations” (http://www.talkorigins.org/faqs/evolution-definition.html). Evolution takes many generations to occur and 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). The vast availability of fast foods and the increased use of machinery is a significant environmental change that has the potential to induce obesity and other diseases that result from a poor diet and lack of exercise. However, one must note that the future generations must also choose not to exercise and eat food too rich in lipids and carbohydrates in order for them to be affected.
ReplyDeleteThe future generations will certainly be at greater risk for heart disease and obesity than their parents (assuming that their parents had an unhealthy diet and chose not to exercise) as recent findings show that prions found inside cells can change shape based on environmental conditions such as temperature or the presence of chemicals. After the prions change shape, they 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. These changes may cause a slowing of metabolism in future generations, which would result in heart disease and obesity only if the future generation continue to maintain the same diet, level of exercise, and lifestyle.
While I agree with Mr. Dash in that the vast availability of fast food and increased use of machinery will certainly have a negative effect on future generations, one must understand that the theory of epigenetics only applies if the future generations make unhealthy choices in their diet and exercise as well. The future generations will have a higher risk for heart disease and obesity than their parents, but one must note that the future generations are not doomed. Lamarck’s evolutionary theory states that “from this habit long maintained in all its race, it has resulted that the animal’s neck is lengthened” (Shenk 156). The giraffe’s passing of epigenetics that kept providing for longer necks occurred because giraffes endlessly faced the challenge of having to reach for foods at higher altitudes. The key phrase is “long maintained in all its race”; as long as the future generations make an effort to eat healthier and exercise, they will lead healthy lifestyles.
- Akshay Ramachandran (ramachandran.akshay11@gmail.com