There were many scientists back in
the early nineteenth century that had their own logic behind evolution. For
example, a French biologist Jean-Baptiste de Lamarck had his own interpretation
of how things evolve, but it wasn’t the best interpretation. Shenk states,
“Lamarckism has been defined as…the flimsy idea that biological heredity can
somehow be altered through personal experience“(155). This statement is very
different from Darwin’s conception of evolution, so use your prior knowledge of
Darwin’ theory and contrast it from Lamarck’s theory seen on pages 155-156.
Also, Shenk states on page 157, “We have long understood that lifestyle cannot
alter heredity” but in 1999, botanist, Enrico Coen, and his colleagues deemed
that statement false. Explain what Enrico Coen did to realize that lifestyle
could indeed affect heredity, and explain the term epigenomes and how it
related to Coen’s experiment/discoveries. Also, refer back to chapter 18.2 and
explain how chromatin modifications relate to epigenetic inheritance and also
give two examples of epigenetic inheritance(page 358 of Campbell).
(Krish Desai) kjdesai5@mac.com
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ReplyDeletePart 1
ReplyDeleteCharles Darwin’s theory of evolution is based on the principle of natural selection in which random mutations create variations within a population and characteristics which are selective advantages enable organisms to pass on their genetic material to their progeny (Campbell 15-16). Lamarck’s general theory postulates that the organism itself is capable of altering the characteristics passed on to its progeny (155-156). Essentially, Lamarck believed that individuals had much more control over what their offspring would inherit. If true, this would not destroy the biological concept and theme of evolution but could potentially completely redefine our understanding of the restrictions that are supposedly set as well as the application of the theory.
Biological research in the mid-20th century discovered the hereditary material known as DNA, which itself is packaged in a chromatin structure (Campbell 321). The arrangement of the histone proteins that form the chromatin structure comprise the epigenome. Enrico Coen and his team studied two different-looking flower that had identical DNA, but distinct epigenomes. Since Coen’s discoveries, other scientists including Marcus Pembrey, who studied the relationship between epigenetics and nutritional deficiencies and smoking, have discovered various character traits and physical conditions that could be inherited after epigenetic changes in the lifetime of the parent (160). Lifestyle choices such as smoking could alter the epigenome, passing on acquired traits. The specific changes made to the chromatin structure include histone tail acetylation which increases transcription and replication at that region by loosening the forces between histones, histone tail methylation which increases the attraction between histones and decreases transcription and replication, and histone tail phosphorylation which counters the effect of histone methylation (Campbell 357-358). While research has not yet conclusively proven the responsibility of epigenetics, research by Dolores Malaspina suggested that “age-related epigenetic changes in human males… can lead to lower intelligence and a higher risk of schizophrenia in children” while research by Megan Hitchins found that there may be “a link between inherited epigenetic changes and human colon cancer” (160). Now, researchers such as Pembrey and Dr. Lars Bygren hope to map out the epigenome to fully understand the implications of inheritance based on epigenetics and improve our understanding of all inherited characteristics and their implications such as inherited susceptibility to certain diseases (http://www.soulmedicineinstitute.org/TimeMag.pdf).
Part 2
ReplyDeleteNew understanding on the effects of epigenome inheritance have profound consequences for our biological theme of evolution. Darwin's widely-accepted theory attributed acquired characteristics to natural selection of genetic variation within a population, allowing a parent to only pass on genes and not actually change the traits. Darwin's theory argues that those with the most suitable traits will survive, while Lamarck's theory argues that individuals can alter their traits to become more suitable to the environment. Nevertheless, the end result is similar; traits and thus genetic material that is advantageous for an organism in a specific environment will be passed on to another generation. While slight modifications to the overall concept of evolution would have to be made, the continuation of advantageous traits still remains central to the theme.
Additionally, the changes in epigenome also reflect the theme of continuity and change. In this case, the gene-environment interaction increases gene expression by altering DNA packaging and chromatin structure. The DNA inherited by the offspring exhibits continuity, but the affected epigenome exhibits change, not only within the parent organism, but also across generations. This continuity and change is closely related to evolution, but is also more applicable on the organism level in which histones are affected to increase transcription (and thus the presence of specific traits) because the environment demands the changes.