In Chapter 2, David Shenk discusses how our specific gene sequences relate to the
environment around us. For example, the genes that are "turned
up/down/on/off" by an "environmental input" determine the
uniqueness of an individual from the moment he or she is born (16). The
external and internal stimuli react with one another to produce this
"custom-tailored human machine" that is specific to the individuals
surroundings. Respond by discussing ways that genes can be specifically
targeted or "switched on, or expressed" in the human body. Also,
discuss the ways that specific environmental situations can impact one's development
or response to one's surroundings. What are some ways that organisms have
developed as a result of specific genes to adapt to their surroundings? Remember
to relate your response to one of the major themes in Biology.
Weronika Dudkiewicz (wdudkie2@students.d125.org)
David Shenk’s whole argument is centered around the belief that genes do not determine your lot in life, because genes are “turned up/down/on/off” depending on “environmental input” (Shenk 16). Individuals are shaped by the environment around them and the stimuli they encounter. This is why individual twins, who in theory should be the same, end up with different personalities and tastes. Although their interests may overlap, dissimilarities are very obvious. A study by psychologist W.J. Wyatt proved that there can be many circumstantial similarities between completely random people (Shenk 81). In the study by Hart and Risley, they discovered that children who lived in professional homes generally were more intelligent and developed quicker than the children who grew up in welfare homes (46). The reason for this disparity didn’t have that much to do with genes or predisposition. The fact was that the difference in amount of words spoken at home, as well as the quality of words spoken at home directly affected the intelligence of the child, as well as the number of encouragements received (47). Some of the welfare children may have been more predisposed to math or English. However, due to the environment that they grew up in, the children in the welfare homes did not have the stimuli to interact with the predisposition. At the same time, some of the children who grew up in professional homes may not have the predisposition to be particularly intelligent. However, due to the encouraging and nurturing environment at home, these children became more intelligent than their welfare home counterparts. This phenomenon is epigenetic inheritance, or “the inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence” (Campbell 358). Rather than dependence on genes, childhood development depends on the environment that they grow up in. Within a nurturing environment, children will flourish. Within a discouraging and unsympathetic environment, children will wilt.
ReplyDeletePART ONE
Annie Lee (xxannie.leexx@yahoo.com)
Similarly, Shenk analyzes the athletic ability of Jamaica. Many people attributed the Jamaican sweep at the 2008 Summer Olympics in Beijing to the gene ACTN3. However, when the American Society of Human Genetics tested for the gene, “no female elite sprint athletes in [the] sample were α-actinin-3 deficient (compared with 8% of males)” and “all male Olympian power athletes in [the] cohort had at least one copy of the functional R allele of ACTN3” (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1180686/). Many people have at least one form of ACTN3. It’s not that particular gene that brings about athletic success; rather, Jamaicans have incorporated running as a part of life in Jamaica, compared to the United States and other western nations, which have an abundance of convenience technology, such as cars, public transportation, and elevators. Jamaicans live in a different environment than Americans, and thus are exposed to stimuli that brings forth the abilities of ACTN3, while Americans can go their entire lives without encountering stimuli that will bring out ACTN3. In Boulder, Colorado, Atlas Sports Genetics is offering a test that will predict a child’s natural athletic strengths by analyzing the presence of ACTN3 (http://www.nytimes.com/2008/11/30/sports/30genetics.html?pagewanted=all). However, although not named within the article, the article brings up a Spanish long jumper who excelled in his sport, who was later found to have no copies of the R variant, a variant of ACTN3 that supposedly predisposes you to power sports. Thus, ACTN3 itself is not responsible for athletic performance. It is the result of hard work, perseverance, and determination.
DeleteOrganisms have evolved to adapt to their surroundings because ingrained in every organism is the instinct to survive and reproduce. Charles Darwin himself studied birds on the Galapagos Islands and discovered that finches adapted their beaks and behavior to the specific foods available on their home islands (Campbell 456). Since many organisms choose their own mates, the organisms that have evolved and adapted are chosen first to pass down their genes, ensuring a higher percentage of survival within their offspring. Truly, the biological theme of Evolution is intertwined closely with Interdependence in Nature. The relationships between the organism and other organisms and the environment brings about evolution, in order to evolve to adapt to the environment. As animals, humans continue to evolve and adapt. This is how and why “every few years, the new batch of IQ test takers seemed to be smarter than the old batch” (Shenk 42). This is due to plasticity, the ability of the human brain to “become, over time, what we demand of it” (36). What we demand of it, however, depends on the environment that we are exposed to.
PART TWO
Annie Lee (xxannie.leexx@yahoo.com)
A person's genome is extremely plastic. This plasticity is caused due to the epigenetic expression of genes. Gene expression can change pretty regularly based on many environmental factors. For example, monkeys that seem to be at a higher level of stress express more immune related genes when compared to those that are living in more luxurious conditions. It was observed for Rhemus monkeys in a social class ranking system that "genes associated with the immune system were more active among low-ranking group members" (http://proquest.umi.com/pqdweb?index=1&did=2630317031&SrchMode=2&sid=2&Fmt=3&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1334158384&clientId=15232). The lower social ranking of the monkeys within their environment translated directly into an increase level of stress. This increased stress thus targets the specific gene sequences that relate to activity of the immune system. The increased immune activity was “switched on” by the level of stress in the environment. This level of immune system activity was not set either. The study revealed that ”immune system activity levels did not seem fixed”. As the environment of the monkeys changed “gene expression changed”. Therefore, the study concluded: “as the monkeys moved up in the world, they became less stressed” (http://proquest.umi.com/pqdweb?index=1&did=2630317031&SrchMode=1&sid=4&Fmt=3&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1334187279&clientId=15232). In total, this study is a perfect example of the plasticity of the genome. The organism adapted based on the environmental conditions that surrounded it.
ReplyDeleteIn continuation of the stressed monkeys, stress causes the production of hormones in the monkeys that affect gene expression. As depicted by the image Shenk uses on page 23, Hormones play a large part on which genes are expressed at which times. Shenk states that “genes are constantly activated and deactivated by environmental stimuli, nutrition, hormones, nerve impulses, and other genes” (Shenk 22). Plasticity of the genome is the best way to describe gene expression. The genes are so greatly affected by internal and external stimuli that changes are constantly occurring in order to adapt to an ever-changing environment. Thus, gene expression is an example of continuity and change. Gene expression is influenced by many factors that expression is always changing. Operons are the face of gene expression change. An operon is what controls gene expression of a certain gene. One type of operon is called a repressible operon. A great example of this is the trp operon which is repressible because “its transcription is normally on but can be inhibited (repressed)” (Campbell 353). Reperessible operons’ opposite, inducible operons, are another type of operon. A common example of this is the lac operon that is “usually off but can be stimulated (induced)” (Campbell 354). Both of these operons are altered when a small molecule binds to a regulatory protein. This means that the genes being expressed are subject to change based on the availability of a certain small molecule.
Sam Alhadeff (alhadeffsam@gmail.com)