In 1932, psychologists Mandel Sherman and Cora B. Key concluded that “children develop only as the environment demands development. (Shenk 41) Explain how Shenk’s G X E model supports this idea through gene regulation. How is the phrase, "as the environment demands development", NOT relating to evolution/natural selection? Also consider how this connects with interdependence in nature. How does biotic/abiotic factors act as stimuli and what kind of reactions do they trigger? Give specific examples and compare/contrast resulting traits.
(Christine Zhao, c_zhao@ymail.com)
(Christine Zhao, c_zhao@ymail.com)
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ReplyDeleteAccording to David Shenk, “genes, proteins, and environmental signals constantly interact with one another, and this interactive process influences the production of proteins, which then guide the function of cells, which form traits.”(31) There are many outside environmental influences that can alter your genes, proteins, and cells. Soem common environmental factors that can alter genes, proteins, and cells are radiation, chemicals, temperature, light, and drugs. In the case of chemicals effecting genes, there was an experiment involving Fundulus heteroclitus eggs that were in an environment of 100 mL of seawater and 6 g of magnesium chloride (http://www.nature.com/scitable/topicpage/Environmental-Influences-on-Gene-Expression-536). Due to the chemicals in the water, the fish ended up with one eye unlike normal fish of that species which have two eyes. In this case, the chemicals present in the environment altered with the fishes’ genes which caused all the fish to have an external trait of one eye. Another example of the environment affecting the organisms’ cells, proteins, and traits is radiation. Radiation can alter the cell cycle by altering the check stations, G2 G1 M, that prevents a cell from being replicated. When these checkpoints no longer function the way they are supposed to, “the cell will keep on dividing and invade other tissues” (242 Campbell). Radiation can cause the cell in a tissue to undergo transformation and if the cell survives the body’s immune system, they will multiply in numbers to become a tumor. These are just a couple of ways the environment can alter genes, cells, and traits.
ReplyDeleteThis changing of genes due to the environment relates to the theme of the relationship between structure and function. This biology theme states that every structure has a different function and minor alterations to that structure completely change the function of that protein. In the case of being in an environment full of radiation, the radiation of the environment can break apart bonds which can change the function of the original protein. Proteins have four structures that allow them to change shape and function. The first structure is the amino acid sequence, which is held together by lots of peptide bonds. These amino acids then twist and turn until they form alpha helixes and beta sheets, which are held together by hydrogen bonds. Then, this secondary structure twists and turns again to create a tertiary structure that is held together by disulfide bonds, hydrogen bonds, ionic interactions, and Van der Waals interactions. Finally, these tertiary structures combine with other tertiary structures to create quaternary structures. For an example of the relationship between structure and function, for the quaternary structures that are enzymes, they can have their structure changed in many ways, which will change their function. If the enzyme were to be heated up to a temperature that it is not used to, the enzyme will denature. Once an enzyme gets denatured, its active site changes shape and the substrate that used to fit in the enzyme can no longer fit. Because the enzyme can’t perform its original task due to a change in structure in the active site, the function of the enzyme changed. Because radiation can alter the structure of proteins, an environment with a lot of radiation is a clear example of how the environment can alter traits.
There are many hormones that are being affected by the environment every day. According to Marianne Kraugerud, steroid hormones that include, testosterone and cortisol are being affected by PCB and PFC which are toxins in the air. These toxins affect the reproductive system and the homeostasis of blood sugar in that they can prevent the production of cortisol which is an important hormone in reproduction and keeping blood sugar levels normal (http://www.sciencedaily.com /releases/2010/07 /100 701081857.htm). This hormone is controlled by the hypothalamus. The hypothalamus releases CRH which tells the pituitary gland to release ACTH which goes to the adrenal gland. This hormone is tells the adrenal glands to release more cortisol in the body to help initiate the formation of lungs in a fetus or increase blood sugar level through glycogenolysis. This hormone can also suppress the immune system by preventing the release of macrophages and other proteins needed for inflammation. This hormone travels through the blood like normal hormones. If this hormone is affected by toxins from the air according to Marianne Kraugerud, the baby will develop with insufficient lungs which is a crucial body trait.
DeleteEric Duresa (eduresa11@gmail.com)
DeleteShenk’s model supports the idea that children develop only as environment demands development because both the environment and genes influence traits in children. As for genes that are inherited, the child receives 23 chromosomes from each parent, having 46 all together. Chromosomes are important because they are an organized structure of DNA and protein. DNA contains many genes and through transcription and translation, DNA is copied into mRNA and then the ribosomes will form proteins from mRNA and tRNA. The proteins that are formed are vital to the body because they can carry out growth and repair, defend against invaders, and catalyze chemical reactions. The chromosomes you inherit from each parent basically determine your DNA and the types of protein and traits you will have. For example, some kids are more easily to burn than others because of the genotype that child has inherited from his or her parents. The environment can also affect children’s development. Different types of environment can turn on or off genes. So when environments are different, some genes can turn off and that specific section of DNA on the chromosome may not be copied at all, and the protein may not be made, causing the child to develop differently. For example, butterflies caterpillars were kept in different lights while others were kept in the dark. When they turned into butterflies, the colors of the wings of the butterflies were dramatically different, demonstrating environment’s effect on gene regulation. The caterpillars raised under red light’s wings were much brighter and more intense than the caterpillars rose in the dark. This proves that environment can influence how traits are expressed. The caterpillars raised in the dark probably didn’t need bright and intense wings because the lighter their wings, the more they will camouflage into their environment, avoiding danger. This adaptation that keeps the butterfly safe is natural selection and the butterfly in the dark environment will be able to survive and reproduce. This occurred because the genes that expressed bright colored wings were turned off thanks to the dark environment. So for abiotic factors, if a kid was raised in a very dark room, then their eyesight might be more sensitive to sunlight because the sensitivity trait expression were probably turned off thanks to the dark lighting. If there is less energy used to develop cones, your body might use more energy to develop rods, which helps you see more in the dark. This goes along with the theory of children develop only as environment demands development because sensitivity to sunlight isn’t necessary to a child raised in a dark environment, and instead of using energy on developing cones, the body will focus more on making rods which will help the child survive in his or her environment. For biotic factors, if a child is raised around musical parents, the parents probably will play music around the house. The child then will develop very sensitive ears to sound because certain genes will be turned on due to that certain environment. Then gene expression will occur where that certain gene is transcribed and translated and copied into mRNA and then into protein. This certain turning on of the certain gene will help the child survive in his or her environment because if child is musically talented, he or she will be able to study music and earn money later on, which will buy them food and shelter. The phrase “as the environment demands development” does not relate to evolution and natural selection because the environment doesn’t demand development and the organisms don’t choose to adapt, natural selection just occurs in the strongest and after a very long time period, evolution then follows.
ReplyDeleteBing Zhao (bingzhao9@yahoo.com)
sources
http://www.nature.com/scitable/topicpage/environmental-influences-on-gene-expression-536
http://www.thetech.org/genetics/ask.php?id=63