In chapter ten (pages 155 to 163) Schenk describes how flowers with the same genes can look different due to the environment and lifestyle provided to that flower. Lamarck was one of the first to suggest an "inheritance of acquired characteristics" and was mocked for what was deemed as" crude, pre-Darwinism conception of evolution" (155). We know now, however, that Lamarck wasn't that far off in his concepts, biologists starting to accept that biological heredity and evolution are very intertwined, and that although natural selection isn't invalidated, it is now a lot more complicated (161).
But how exactly can ones life style affect their heredity? Can your perfecting a talent make it easier for your children and grandchildren to also learn that skill? Or can bad choices, such as substance abuse or lack of any higher education affect your descendants 2, 3, 4 generations down the line? How intertwined can lifestyle truly be with our evolution as a race?
(kenny@shimanek.org) Kenny Nelson
Lifestyle can effect heredity because of the epigenome. Changes in the packaging that surrounds the DNA (the epigenome) can alter the phenotype of plants an animals. For example, Shenk discussed how the toadflax plant could have very different flowers despite having the same genes if their epigenome was different (Shenk 158). This is because histones, which protect the DNA and make it compact, are "a mediator for gene expression "Shenk 158 ). The toadflax flowers passed down their epigenetic traits to their offspring, which provides evidence that organisms DO inherit epigenetic traits.
ReplyDeleteBad lifestyle choices can effect heredity. One aspect of lifestyle that effects heredity is the environment in which an organism lives. For example, Shenk mentioned on page 160 that rats that were exposed to pesticides had at least four generations of offspring with a low sperm count. Additional lifestyle choices, such as smoking and poor diet can also cause people to pass on unfavorable traits. For example, changing the diet of a pregnant agouti mouse can determine as to whether or not the agouti gene will be expressed, causing the offspring to have much shorter lives (http://discovermagazine.com/2006/nov/cover).
In addition, positive lifestyle choices can also cause an organism's offspring to inherit the benefits of those choices. For example, young mice placed in a stimulating environment improved their own memory and also improved their offspring's memory. This indicates that "parental behaviors that occur long before pregnancy may influence an offspring's well-being" (Shenk 162). This indicates that lifestyle is very intertwined with evolution. People who live in bad environments or make bad lifestyle choices, like smoking at eating poorly, are more likely to produce, dumber, less fertile, and disadvantaged offspring than people who make better lifestyle choices, like studying more, eating right, and living in a healthy environment.
Laura Perlman (laura4@comcast.net)
Campbell mentions that Darwin never used the term evolution in his famous Origin of Species book. Rather he talks about “descent with modification”, which means that he believes that all organisms come from a common ancestor and over the course of millions of years they “had accumulated diverse modifications, or adaptations, that fit them to specific ways of life” (457). Along with this concept was the fact that lifestyles cannot alter genes. As Shenk says, “any high school student knows that genes are passed on unchanged from parent to child” (157). But epigenetics says that is not the case.
ReplyDeleteThe University of Utah says that epigenetics is not something we can ignore. They say despite the fact that epigenetics is still new and hard to detect, there is still evidence for it. An example using humans is a pregnant mother. Gestational diabetes is a hormone triggered diabetes in mammals that can occur during pregnancy. “When the mother has gestational diabetes, the developing fetus is exposed to high levels of the sugar glucose.” This of course means that the child will have a greater chance of developing gestational diabetes. The example illustrates that epigenetics is real, but is a significant factor. That is yes and no. In a pregnant mother, “three generations are directly exposed to the same environmental conditions at the same time” but at the same time in the formation of an embryo epigenetics tags are removed through a “reprogramming” process with “about 1% of genes escape epigenetic reprogramming”.
(http://learn.genetics.utah.edu/content/epigenetics/inheritance/)
Even if only a few epigenetic tags remain, they do still have an effect on future generations. While it’s clear to see how a pregnant mother can affect the genetic imprinting of her child, is possible before pregnancy or for men to affect their children’s epigenetic inheritance? The answer seems to be yes. Shenk talks about an experiment on page 162 from the Journal of Neuroscience that found that “the improved memory of young mice with a memory-impairing genetic defect… improved the memory of their eventual offspring.” If experimental results on rats say anything about humans, and they do which is why we do them, then the act of improving your own skills can have an effect on your children and grandchildren. As Shenk puts it, the idea that “a twelve-year-old kid could improve the intellectual nimbleness of his or her future children by studying harder now” would be laughable twenty years ago but “today, that preposterous scenario looks downright likely”. (161-162)
Laura, while you are correct in saying that a positive environment will produce offspring with more of an evolutionary advantage than a bad environment, there are two more concepts I would add. The first being that natural selection works with the environment. While you could say a shark is a better predator than a housecat, these organisms have distinct advantages in their own environments that would not help them in survival in each other’s environments. So even with people, if some can change their habits along with their environment, they will assist their future descendants in terms of epigenetics. The second is that epigenetics is still a new field so it’s hard to say for sure what is beneficial. In your agouti mouse example, the different diets affected the epigenetics of the offspring. But in humans, it’s hard to say what lifestyle will have what affects on the offspring and which would present a higher evolutionary advantage. An example being focusing on studying versus focusing on athletics or balancing both is some way. The epigenetic effect can only be considered an evolutionary advantage if it helps the offspring pass down his or her genes to the next generation in his or her environment.
Alvin Varghese (alvin.varghese@hotmail.com)
An individual has the power to change the genes that he or she inherits. It has been proven through a variety of experiments that the outer packaging of a gene called the epigenome can be altered from environmental factors. The epigenome acts as the trigger to either turn the gene on or off. A French biologist named Jean-Baptise de Lamarck was the first one to discover “than an individual’s actions can alter the biological inheritance passed on to his or her children” (Shenk 155). Enrico Coen, a botanist, conducted an experiment trying to find the genetic differences between two types of toadflax. One was a newer and rarer type called the Peloria while the other was the ordinary toadflax. He discovered that both types of toadflax had the exact same genetic code, but their epigenomes were different. It was proven that the Peloria passed down this altered epigenome through generations so that their offspring expressed this altered form. This proves that lifestyle can affect heredity because the lifestyle of the toadflax changed it’s epigenome which got passed down to their offspring.
ReplyDeleteSince lifestyle has been proven to affect heredity, the choices an individual makes throughout his or her life will indeed affect their children. If an individual perfects a talent or makes bad choices concerning drugs and alcohol, this new addition may indeed be passed on to future generations. “If what happens to you during your lifetime – living in a stress-inducing henhouse, say, or overeating in northern Sweden – can affect how your genes express themselves in future generations, the absolutely simple version of natural selection begins to look questionable” (http://www.guardian.co.uk/science/2010/mar/19/evolution-darwin-natural-selection-genes-wrong). Since lifestyle can affect your epigenomes which will affect your offspring, the simple Mendelian genetics has alterations. Charles Darwin stated that individuals inherited all their traits from their parents and were not susceptible to change. However, as more research comes out, this fact is wrong because lifestyle can now affect the future generations of the world.
The concept of evolution supports Lamarck’s claim that lifestyle can affect heredity. Evolution is the “scientific explanation for [the] unity…diversity…and the suitability of organisms to their environments” (Campbell 3). There are millions of different types of organisms in the world that have evolved from other organisms in order to adapt to their current environment. The only way this change could’ve happened was if they passed it down to their offspring. Lifestyle is definitely a core factor in the process of evolution that drives the success of the human race.
Anisha Ghosh (anishaghosh16@gmail.com)