Shenk clarifies the idea of gene expression in footnote 19, where Moore explains that gene expression is influenced through several mechanisms and that experiential factors that influence gene expression can be "turned up/down/on/off at any time-- by another gene or by any miniscule environmental input" (183). This evidence is an example of gene-environment interaction (GxE).
Given this information and what you already know about gene expression, discuss how this demonstrates that an organism's phenotype is an example of interdependence in nature. What significance does GxE hold for for diseases such as Type II Diabetes where an individual is more susceptible to the disease in a particular environment due to genetic factors? How does GxE relate to the concept of epigenetics?
-Jessica Hua (jhua33@yahoo.com)
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ReplyDeleteAn organism's phenotype is regulated by what genes are expressed; the expressed genes reveal visible traits such as hair color, eye color, and body type. Campbell defines "differential gene expression" as "the expression of different genes by cells with the same genome" (356). This means that, even though all somatic cells have the same set of genes, different bodily and environmental factors determine which of those genes will be expressed, reflecting our interdependence with nature. Genes more often interact with nature to determine which genes will be repressed rather than expressed, as a "typical human cell probably expresses about 20% of its genes at any given time" (Campbell 356).
ReplyDeleteResearchers have known that diseases such as diabetes are affected by both genes and environmental factors, and the GxE model reinforces the need to study associations between diabetes and various environmental factors. Fr example, researchers at Stanford University have discovered strong associations between diabetes and high levels of a form of vitamin E found in fruits, vegetables, nuts, and milk. They have also found a correlation with PCB's, a synthetic chemical used in manufacturing. Identifying these environmental factors in our daily lives can help decrease the likelihood of people that are already genetically susceptible from getting diabetes.
(http://www.sciencedaily.com/releases/2010/05/100520212615.htm)
Expression of genes is not limited to interference with DNA itself: histones, the packaging of DNA, can also regulate expression. Processes such as histone acetylation, in which acetyl groups are added to the histone tails, can promote transcription (Campbell 358), and the initiation of histone acetylation can be triggered by environmental factors. The dynamics of GxE can affect both the DNA and chromatin, and makes gene expression much more complex.
-Akila Khan (starlight608@gmail.com)