In relation to Big Idea 3, which is “Living systems store, retrieve, transmit, and respond to information essential to life processes”, Dr. Moalem writes about epigenetics with fetal development from pages 162-165 and how the first few days after conception can have a huge impact on the growth of the fetus after once it’s born. Dr. Moalem uses the example of childhood obesity being a result of bad nutrition of the mother which are epigenetic signals for the fetus. Explain how bad nutrition in pregnant mothers today lead to children becoming obese. Define the term “epigenetic” and “phenotype” in your answer. Afterwards, research another medical condition that could be a result of epigenetics in fetal development and explain how that works.
(Jenny S. Li - jesli4@students.d125.org)
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ReplyDeleteAccording to Survival of the sickest, if a pregnant women has junk food diet during the first few weeks of pregnancy, this can lead to the baby being born small. The mom’s body will assume from the diet high in calories but low in nutrients, that the child is being born into a environment with a low supply of food, so it would want the baby to be able to survive with less intake of food. The child will be born with a metabolism phenotype that is more efficient at hording food. This phenotype, or the physical expression of the genotypes, would have been useful many years ago during famines. But in the 21st century where food is abundant, when the epigenetic markers turn on this phenotype of the genotype, than the child will most likely become obese. Epigentics is the change of gene expressions without changing the actual DNA, which happens by adding methyl markers to DNA or histones to inhibit transcription.
ReplyDeleteAsthma is another medical condition that can be the result of epigenetics in fetal development. Asthma can be increased by the epigenetic markings from environmental factors, like cigarette smoke or pollution. In an experiment with rats, the first generation of rats was exposed to nicotine and produced asthmatic pups. The 3rd generation of pups was also asthmatic, but the 2nd generation had no further exposure of nicotine. Virender Rehan, who conducted a similar study, blames epigenetics and the acetylation of histone 3. Smoking can also lead to many other health problems for the human babies when they are born, like a low birth weight and increased risk for disease. Smoking will pregnant can lead to altered DNA methylation and a mutated formation of microRNA. DNA methylation is when a set of enzymes methylate certain bases in DNA to stop transcription by inhibiting the binding of RNA polymerase II , part of the transcription initiation complex to RNA and other transcription factors. DNA methylation occurs in patterns that are passed down generations; if this pattern gets altered then the methylation may not occur in the embryo leading to complications. One complication could be if a fetus has a birth defect known as MTHFR. Normally, an insulin-like growth factor would get methylated, but in this case it does not and leads to neural tube defect in the fetus. This cause for the nutrients needed for the survival of the fetus to not reach him or her. (http://www.brighthub.com/science/genetics/articles/59055.aspx ) MicroRNA also leads to the prevention of translation, by the creation of miRNA from pin shaped RNA strands. The process RNA interference can silence gene expressions. MiRNA mutations may lead to the child having schizophrenia as they grow older. (http://www.cityofhope.org/about/publications/eHope/2009-vol-8-num-8-august-20/Pages/microrna-mutations-may-be-to-blame-in-mental-illness.aspx) Thus, smoking can cause a multitude of problems for the fetus of a pregnant women and the women.
(http://www.the-scientist.com/?articles.view/articleNo/33123/title/Dangers-of-Second-Generation-Smoke/ & http://www.ncbi.nlm.nih.gov/pubmed/23062304)
(lbarghi4@students.d125.org)
According to the Epigenetic researches such as one conducted in the small village in Sweden suggests that the allele of the fetus can be changed when the mothers are exposed to various different environment. One of such environment is the hunger or poor nutrition in this study. Expectant mothers' exposure to such environment will cause developing fetus to express the genes that will cause them to gain weight(which is the phenotype of that particular gene). This is not the absolute relationship where that kind of environment cause the obesity all they time. However, such gene expression becomes frequent bough so that people can acknowledge that fact and can report as the official scientific paper. In this 21 century where people have very easy access to poor but rich nutrients have same problems as the starved people do.
ReplyDeleteOne of example of epigenetics that occurs to fetes is the expo rue to alcohol; since the alcohol is the extreme toxins, it can distort the correct gene expression that is necessary for the development of nervous system and development in facial features. This is the specific cause of Fetal Alcohol Syndrome, whose symptoms are slowed development in nervous system and slightly deformed facial features. Some of such conditions can be inherited but the rate of expression of such gene can vary through generations. (http://pubs.niaaa.nih.gov/publications/arh341/29-37.htm).
The epigenetics is the study of such pattern of gene expression, and as Lily mentions, their greatest work is the breakthrough on the eukaryotic gene expression. it was discovered that microRNA is used to regulate the gene expression through RNAi. Sometimes, the methylation and acetylation can cause such regulations. The other great factor that controls the gene expression i humans (or other mammals) is the transcription factors, and it is directly responsible for the rate of transcription thus it can determine the rate of gene expression. The famous example is the way to induce pluripotency for iPS cells. The group of genes which is commonly known as Yamanaka factors will induce pluripotency to the cells which is already specified. Some of such factors includes genes that creates transcription factors. The details of how such factors work is still unknown, but scientists are confident that the gene regulations have some great applications such as inducing pluripotency. (http://www.stemcellsportal.com/news-and-press/latest-news/218-yamanaka-factors-version-20-.html)
Makoto Seita (mseita3@studnets.d125.org)
With the discovery of epigenetics, it became clear that things a mother does while pregnant, or even before she becomes pregnant, will have a huge impact on the genetics of her child. On page 161, Dr. Moalem explains that with epigenetics, "the DNA doesn't change-- but the way it's expressed does". Environmental triggers will change how genes are expressed without actually changing DNA.
ReplyDeleteFrom pages 162-165 in his book, Moalem describes how poor nutrition of a pregnant mother could lead to child obesity. From an evolutionary viewpoint, this makes sense. Our ancestors 1000s of years ago had a very unstable environment. There was a very good chance that they would be born into a drought or famine. For this reason, if a mother has poor nutrition during pregnancy, the child will sense that it is being born into a period where nutritional food is scarce. As Moalem mentions on page 163, a medical professor named David Barker came up with the Barker hypothesis to explain this. This hypothesis, also known as the thrifty hypothesis, states that "fetuses that experience poor nutrition develop thrifty metabolisms that are much more efficient at hoarding energy" (page 163). 1000 years ago, a "thrifty metabolism" would help a person survive. However, today this low metabolism makes it harder to burn calories, and could lead to child obesity. As lily mentioned above, a phenotype is the physical expression of genotypes. Epigenetics will methylate or acetylation to turn on or off or the genes. Lily also mentioned that although the mother may eat poorly, the world that the baby will be born into is not low on nutrients. When a fetus is exposed to poor nutrition from their mother, epigenetics will turn the gene for the thrifty metabolism on and the child will likely become obese when they are born into a world where nutrition really isn't scarce.
Another condition that results from epigenetics during fetal development is asthma, which results from smoking. As Dr. Moalem says on page 166, a research team in California discovered that the children of Grandmothers who smoked were likely to develop asthma. This suggests that epigenetic markers skip generations by turning on or off genes that will be in their daughters egg supply. In this study, these researchers used rats and injected them with nicotine when they were pregnant. The offspring of these rats were shown to have asthma. They were allowed to mature and breed, but without injection of nicotine, and their children also developed asthma. This showed that the nicotine was effecting the expression of genes in the eggs of the second set mothers. It also proved that epigenetics can last for more than a single generation. (http://www.economist.com/news/science-and-technology/21565573-some-effects-smoking-may-be-passed-grandmother). In another study, published in Human Molecular Genetics, the "epigenetic footprint" of smokers was compared to nonsmokers. The smokers had less methyl groups on 20 different regions of their DNA. These regions had previously been linked with cancer. (http://news.sciencemag.org/sciencenow/2012/12/smoking-smothers-your-genes.html). This shows that smoking may change a person's gene expression and make it more likely for them to get cancer. Even more so, Dr. Jean-Pierre Issa explains that smoking is toxic to cells. He says that "anything that might injure tissues might lead to epigenetic damage". Every time a cells needs to repair itself, it ages, which causes the person to age. (http://www.pbs.org/wgbh/nova/body/epigenetic-therapy.html) So if a person smokes a lot, they will not only put their grandchildren at risk for asthma and put themselves at risk for cancer, but they will likely age much quicker than most people.
Epigenetics relates to Big Idea 3, which is “Living systems store, retrieve, transmit, and respond to information essential to life processes”. Our bodies respond to environmental factors to change the way our genes are expressed.
(Julianna Holzer-jholzer4@students.d125.org)
During the start of a females gestation period may the most important for determining the trait of an offspring according to Doctor Moalem because it is during this period that important genes can either be turned on or off depending on the mother’s lifestyle. Particularly in the case of childhood obesity, the amount and type of food a mother consumes during her pregnancy actually determine the ability of the child to become obese. When pregnant mothers consume foods which are high in calories and fats but low in nutrients, signals will be transmitted into the developing fetus to indicate to it’s body that it will be born into a harsh environment probably full of famine. These signals results in the induction and repression of certain operons which causes particular genes to be either turned on or off. This changes the genotype of fetus and while RNA is being translated, the phenotype, or expression of a trait(www.biology-online.org/
ReplyDeletedictionary/Phenotype), of the baby is a small body so it will need less food to survive in the harsh environment.Such a trait would have helped the population to be able to survive harsh famines in the past such as the Great Famine of 1315-1317 in Europe. Individuals who obtained smaller bodies who have not had to obtain a lot of food in order to survive so this characteristic would have become an adaptations for that period. And individuals with that trait would have been able to survive and reproduce in the human population. This relates to Big Idea 1: The process of evolution drives the diversity and unity of life. But just as both Lily and Makoto indicated, that trait would not be beneficial to the offspring but would rather cause obesity to the child.
Epigenetics is maintaining homeostasis and aiding development in an organism through chemical reactions that switch parts of the genome off or on at strategic times and locations. And epigenetics includes studying these reactions and the factors that influence them (http://learn.genetics.utah.edu/content/epigenetics/). One disease which could arise due to changes of the genome of a fetus is cancer. When there is not enough methylation in the DNA, chromosomes become and instable and there is also activation of oncogenes which causes cells that are supposed to die to survive and proliferate instead. But too much DNA methylation initiates the silencing of tumor suppressor genes. Heavy metals such as cadmium disrupts DNA methylation. Smoking also stimulates the demethylation of metastatic genes in lung cancer cells. And inadequate intake of folate and methionine, which are both used in cellular processes that supply methyl groups needed for methylation, can affect the expression of growth factor genes.
(http://oehha.ca.gov/public_info/lecture/epigenetics.pdf)
(Prince Morkeh pmorkeh4@students.d125.org)