Moalem mentions on pages 157-160 the concept of epigenetics and how the agouti mouse experiment has proven how the concept of epigenetics works. Essentially, epigenetics is referring to modifications in the genome that does not change the actual nucleotide sequence (some examples of changes like this are DNA methylation and histone modification). Moalem also brings in an example on page 156 about how it is possible that the bad dietary habits of pregnant women may impact the metabolism of their children, which means that the eating habits of the mother may modify what genes will be expressed in the child.
This relates to big idea 4, which states biological systems interact, and these systems and their interaction possess complex properties. Epigenetics essentially is the idea that the interactions people have with their environment shapes what genes would be expressed in the individual, which once spurs on the famous “nature vs. nurture” debate.
However, modern scientists actually believe that epigenetic changes are not a large factor in long term evolution. Research why scientists believe this assertion is true and analyze why this is better than if epigenetic changes are a large factor in long term evolution.
(Aaron Chai, achai4@students.d125.org)
Modern scientists inherently believe that epigenetic changes do not have long-lasting impacts on evolution in the long run. Although the experiments on the agouti mice proved that genetic blueprints were unchangeable, "these factors didn't change the DNA the baby mice inherited, but [simply[ in changing the way the DNA was expressed, they changed heredity." (page 160, Moalem) Thus, epigenetics wouldn't be a large factor in evolution as the only thing that's changing about the infant mice's genetics are the way the genes are being expressed. If the genes were being changed, (as how mutations would affect DNA), then epigenetics would have had a larger role.
ReplyDeleteArticles from the site ScienceDaily also support the belief that epigenetic changes do not have long lasting impacts. In one article (site given below), researcher Jorg Hagmann quoted "New epimutations (changes in phenotype or gene expression) are often not maintained over the long term. Only when selection wins out... can these epimutations affect evolution." (ScienceDaily, Hagmann). Simply put, changes resulting from epimutations normally don't have any selective advantages that keep the trait constantly appearing in the population, and thus does not impact evolution as the trait is not guaranteed to reappear in the next generation.
The fact that epigenetic changes do not overly impact evolution is more beneficial than if epimutations did because epimutations do not always guarantee a selectively advantageous trait. If environmental factors caused an organism to produce an infant with epimutations that weren't beneficial, then the resulting organism would be selected against and not be able to survive and reproduce.
Epigenetics relates to Big Idea 4, in that biological systems interact. The biological systems that interact within epigenetics would be the environment and the reproducing organism, in that outside factors determine what genes will be expressed. These combined factors produces complex properties that may or may not be beneficial for evolution.
Tony Chung
kchung4@students.d125.org