-The Argument
David Shenk proposes that “bodies are primed for plasticity” and “built for challenge and adaption” (131). Recall our study of gene regulation with trp and lac operons in E. coli and describe any connections to Shenk’s statement on the plasticity of organisms. Our bodies specifically go through “an activity-dependent process at the molecular, cellular, and organismal levels involving probabilistic epigenesis” (131). Shenk stresses that while we are born with certain characteristics and different appearances, the role of epigenesis ultimately enables people to change through experience and therefore produce “pianists, novelists, botanists, or marathoners” (131). How can we relate Shenk’s assertion to cell fate determination and organizers described during the animal development unit? In addition, how does divergent evolution play a significant role in the plasticity of organisms? Consider how the wing of a bird, the fin of a whale, and the arm of the human all differ in structure and function, yet all arrive from a common origin. Describe the relationship of an organism’s plasticity with the biological theme of evolution.
-Trish Chari (trishtennis@gmail.com)
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ReplyDeleteOur “bodies are primed for plasticity” and “built for challenge and adaption” (131), and the trp and lac operons in E. coli relate to our gene regulation and our ability to be “plastic” for adapting to the environment. Although the operon is a system in prokaryotic cells, the regulation is an important relation to humans because clusters of genes which code for protein are regulated. When tryptophan is present it acts as a corepressor and it activates the repressor protein which blocks transcription (Campbell 353). Meanwhile for the lac operon, when lactose is present lactose acts as an inducer and inactivates the repressor, allowing the enzymes for lactose utilization to be used (354). These systems are proof of the plasticity of organisms because they are capable of regulating the expression of genes based on the interactions with the environment. Gene expression is usually tied with transcription for bacteria and eukaryotes, but the complexity of eukaryotes allows more opportunities for regulating gene expression at more stages. For eukaryotes, our bodies are built to be “plastic” through our ability to regulate gene expression at almost any stage including chromatin modification, transcription initiation, RNA processing, translation, mRNA degradation, and protein processing. Typical human cells probably express about 20% of its genes at a given time, and gene expression is like “giant control board inside every cell of your body” that “can be turned up/down/on/off at any time” (19). Gene expression regulation is a perfect example of the human body’s “plasticity” as the subset of genes expressed in the cells of each type is unique, allowing the cells to carry out their specific functions.
ReplyDeleteMeanwhile for animal development, cell fate determination and organizers only create the physical structure of organisms through epigenesis. Cells in a developing embryo respond to positional information. Organizer regions of the embryo, such as the dorsal lip of the blastopore in the amphibian gastrula, send information in the form of signaling molecules. The signaling molecules influence gene expression in the cells that receive them leading to differentiation and structure development (Campbell 1045). Ultimately, epigenesis determines gene regulation from development while the environment tests the “plasticity” of an organism even more by changing gene regulation in an organism through experience.
Divergent evolution is another example of the “plasticity” of organisms because divergent evolution can either add to the original function of a structure or change it completely. In order to adapt to environmental conditions, two groups develop into distinct species and different functions of a structure will be necessary in order to survive and reproduce (http://science.jrank.org/pages/2609/Evolution-Divergent.html). The common origin of structures from the wing of a bird, the fin of a whale, and the arm of the human all have different functions because that is how evolution caused a natural selection of organisms that have structures with the correct function for their environment. By adapting to the environment, the theme of evolution relates to the “plasticity” of organisms over time as the structure and function can change accordingly over time and through evolution to the survival of the organism.
(Kirk Chiu- krkpchiu@gmail.com)