Two different types of toadflax flowers where determined to
have the same genes but very different appearances or phenotypes which was
found to be the result of differing “epigenomes
– the packaging that surrounds DNA” (157-158). How can differing epigenomes
lead to different levels of gene expression? What are some ways to alter our
epigenomes that will have an effect on generations to come?
Lizzy Ettleson, lettleson@gmail.com
The two different phenotypes or appearances that resulted from two genetically identical toadflax flowers as a result of epigenomes are a perfect example in support of Shenk’s idea of GxE. These differing phenotypes are a result of having different epigenetics. Epigenomes are the packaging that surrounds the DNA. These epigenomes can be changed by the environment, and is, therefore, “an important mechanism for gene-environment interaction” (Shenk, 159). What this demonstrates is that the environment has a perceptible impact on the traits that we express. This idea makes the evolutionary process a more “interactive” one (Shenk, 161). However, a unique trait that wasn’t discovered until 1999 about epigenomes is that, epigenomes can actually be inherited from one generation to the next. Epigenetic inheritance is due to modifications in the chromatin that are passed down, and they do not directly involve the nucleotide sequence. Chromatins, which are DNA of eukaryotic cells and proteins packaged together in an “elaborate complex,” packs a cell’s DNA in order for it to fit inside of the nucleus but it also assists in regulating gene expression (Campbell, 356). These chromatins can also be modified. They do not cause a change to the actual DNA sequence, but these modifications could be passed on to future generations. This is the phenomenon known as epigenetic inheritance. However, these same modifications can be reversed (Campbell, 358). These modifications can be “turned on” or “turned off.” Thus, epigenetic inheritance is heavily dependent on the environment, which supports Shenk’s idea of the environment playing a huge role in the traits we express.
ReplyDeleteDiffering epigenomes do, in fact, lead to different levels of gene expression. Similar to how the two genetically identical toadflax flowers had different appearances, many twins with the same genetic sequence have incidences where one twin acquires a genetically based disease such as schizophrenia, bipolar disorder, and cancer while the other does not (http://www.nytimes.com/2005/07/05/health/05gene.html). Epigenomes make it possible for the genome to essentially be responsive to the environment. Thus, from genetically identical twins to genetically identical flowers, epigenomes turn certain traits on and off in response to stimuli in the environment. These modifications to the chromatins are what allow for different levels of gene expression, certain genes are expressed while others are not.
There are many ways to alter your epigenomes for future generations to come. Start with the most basic such as having a healthy diet. It sounds a bit ridiculous, but this could have a major effect on your children and your grandchildren. For example, it was found that, many school children have high blood pressure and low HDL, good cholesterol, which was a result from the poor diet choices of their parents (http://www.beinghealthynaturally.com/health/geneticcode.php). Improving your diet and health could allow many proteins in your genes to turn off genes that would have been expressed as diseases in your descendants. Sometimes, having a challenging environment isn’t necessarily bad either. For example, in a study done by Dr. Bygren, a study of the effects of famine on a generation and that generation’s descendants which controlled for socioeconomic variations, it was found that the grandsons of boys who had overeaten died an average of 32 years earlier than those that had endured a poor harvest (http://www.time.com/time/magazine/article/0,9171,1952313,00.html#ixzz1rnCGAPJ2). Those boys who had survived a poor harvest and endured the hardships had grandchildren that had a longer life. This does not mean you should starve yourself, however. There are many ways you can improve your epigenomes for your descendants; the most you can do is try to live a happy, healthy life.
(Yanfei Gao, feifeiyg@yahoo.com)