On pages 160-161, Moalem discusses the effects of epigenetics on the characteristics of newborns from different species in relation to the environment they are born in. It seems that the environment the mother is experiencing has a direct effect on the phenotypes its offspring displays. For example, a female vole depends on the amount of light it can sense to tell the whether patterns, and depending on the season when she gives birth, the newborn voles will either have thick or short coats of fur. This relates to Big Idea 3 and 4. The methylation of DNA, or turning them on and off, determines whether a phenotype is expresses. Transcription is regulated this way, so if certain genes aren't transcribed, the proteins they code for will not be synthesized. This would cause the absence or presence of certain phenotypes. Also, the methylation in the fetus' DNA is from the mother's responses to the environmental conditions around her, and it provides her babies with a better chance at survival and reproduction.
Pick a species of animal that has exhibited this sort of epigentically controlled offspring phenotype selection, and discuss two or more possible environmental conditions a mother would experience that would affect the characteristics of her babies. Describe these characteristics and how they would be advantageous in the newborns' survival. Also, discuss how the genes for those particular phenotypes could be altered in response to a mother's environment. (ie. methylation or demethylation turns genes on and off which results in a thick or short coat) You may select one of the species mentioned in the book, but please research on a characteristic not explained in it. (ie. thick coats of voles due to variation in amount of light is off limits.) However, you may also find a species not mentioned in the book as well.
(Vivian To vivto4@students.d125.org)
Environmental conditions as well as nurturing are major components in determining characteristics and behaviors of the common rat by affecting the rat’s epigenome. The most notable characteristic determinant of the common rat is the way it was nurtured as a baby. The amount of attention a mother gave its offsprings significantly determined whether they became docile or stubborn. It was noted that rats that received a constant maternal licking were shown to have reduced stress levels, and fared better as adults. On the other hand, offspring that received less attention and therefore less maternal licking were found to have higher stress levels and restlessness. These differences occurred because the maternal licking, which is basically grooming, lowered the levels of carticoid gene expression which is responsible for producing the stress hormone. So therefore, more grooming meant more DNA methylation which was responsible for preventing the stress related hormone from being produced. With the absence of stress, rats were calmer and more in tune with their environment. Researchers developed a cure in which the chemical TSA was given to the restless rats and effectively reversed DNA methylation.
ReplyDeleteOn page 164 Moalem also describes a study in which pregnant rats were fed a diet with little protein. The finding was that their offspring were much more likely in developing high blood pressure. The most disturbing part is that the low protein diets were administered for only the first four days of pregnancy, showing how rapid changes to the epigenome are.
Not only do epigenetic changes occur during adolescence, they can also occur during adulthood. A test in which rats were exposed to aggressive neighbors (other rats with aggressive behavior) were shown to have dramatic behavioral changes. They were seen to avoid socialising and appeared to be ‘defeated.’ This essentially mimicked depression in humans. This was due to the fear instilled into the rats from the aggressive neighbors, which then altered the histones causing inappropriate gene expression. Researchers also found that giving the rats antidepressants was able to cure them of their social avoidance.
While the circumstances stated above have no real advantages to the rats, they do play a crucial role in determining how certain environmental conditions alter our epigenome. Once the environmental triggers are found, we can find a way to reverse the changes made so that favorable conditions can be instilled. The fact that cures were found for both situations show that this type of research could lead to the prevention of many diseases by methylating or demethylating specific genes and altering our epigenome. This related to Big Idea 3 and 4. Now, on page 160 Dr. Moalem notes that, “... the ability of some organisms to produce offspring that seem to be custom-tailored on the basis of the mother’s experiences during pregnancy” is well known. This is especially important because we have a preliminary understanding of developing, “... healthier, smarter, better babies” (Moalem 162). Although the mother has a large influence on the epigenetic outcome of its offspring, it is important to understand that these “custom-tailored” offspring are not only affected by the mother’s experiences, but also the organism’s own experiences as well. These experiences will influence the organism’s characteristics throughout their lifetime. Through this, we can purposely alter our epigenome to control our health.
Sources: http://abcnews.go.com/Health/Depression/story?id=4839669&page=2#.UW3yS2OnbD1, http://www.environmentalhealthnews.org/ehs/news/epigenetics-workshop
(Ted Nowak, tnowak4@students.d125.org)
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ReplyDeleteOn page 161, Moalem describes how desert locusts' characteristics change depending on the environment the locusts born in. When food is scarce, locusts are born with a color for camouflage that will help the locusts to hide from predators. When food is abundant and the locust population is large, locusts are born with more noticeable, bright color to help the locusts to find each other and interact/mate with each other.
ReplyDeleteThe fact that the environment can have a huge influence on the phenotype of a locust relates to the big idea 3. The big idea 3 states that gene expression is effected by environmental signals. Clearly, the locusts’ expressed gene of their color is determined by their environment at birth.
The expressed genes of different locusts are determined by methylation of DNA. The methylation of DNA is influenced mainly by the mother’s environment whether the environment is crowded or isolated. Compared to the locusts in solitude, locusts in a very crowded environment tend to walk and move a lot more. Most importantly, the locusts in a crowded environment groomed more frequently. More grooming led to more methylation of DNA to oppose stress hormone for the offspring, leading to brighter color being expressed. This sequence is similar to how rats' grooming lead to DNA methlyation. Also the locusts tend to stick together, touching each other often. This behavioral change caused by the environment’s signal causes some genes to be expressed while some genes to be turned off. In this case, lots of movement and grooming of mother causes bright color to be expressed for the mother’s offspring. An environment of solitude and not much grooming give darker color for locusts.
woosik choi (wchoi3@students.d125.org)
http://www.nature.com/hdy/journal/v106/n2/full/hdy201068a.html
http://authorservices.wiley.com/bauthor/onlineLibraryTPS.asp?DOI=10.1111/j.1744-7917.2012.01518.x&ArticleID=990586
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3230539/