-Kyle Nelson (kynels21@gmail.com)
Friday, April 13, 2012
The Evidence - Fruit flies and epigenetics
David Shenk mentions how "A single fly's random genetic mutation can spread into a whole community in a matter of months. Scientists have demonstrated this many times over..." (Shenk 174). As Shenk says it is much easier to spread mutations throughout a fly population because they reproduce so quickly, but he also makes an argument in chapter 10 on how the epigenome of an organism can take a huge effect in its life. As a fly's life span is so short though, would epigenetic changes have time to take effect in a single generation or would any epigenetic changes take place over multiple generation, at about the same rate a mutation in a population can spread? And if this is so then would a single fly population be changed in phenotype more by epigenetic inheritance or evolution through random mutations, selective advantages, and natural selection? Relate your response to the theme of evolution and also use information from Campbell of epigenetic inheritance ( chapter 18 section 2) and evolution through natural selection.
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As defined by the NCBI, epigenetic inheritance is “heritable alterations in which the DNA sequence itself is unchanged.” In asking if epigenetic changes would have time to affect a single generation, it is important to remember how long certain processes take to complete. As soon as the protein is made in the altered form, a small body— like that of a fly—would allow for quick transfer of the new protein to its destination and the change would take place. Thus, in response to whether an epigenetic change has time to effect a single generation, it can because these processes don’t take that long. However, in response to the second part of that, asking if epigenetic changes would take place over multiple generations, I would say they would. To clarify, I do mean that both are possible and both commonly occur, but different types of epigenetic changes occur depending on the environment that forces these changes. Some genes in a fruit fly may code for proteins that may aid in foreign environments so if, for example, a fly native to Florida was released into Arizona, this fly would be able to adapt to the heat and environment change that came with the move. This sort of change is also visible while the epigenetic changes themselves can only occur in each individual organism’s life, an accumulation of epigenomic changes may lead to a significant change or improvement in the species involved. It is recognized that “mutations in the DNA are permanent changes, [while] modifications to the chromatin can be reversed” (Campbell 358). This means that epigenomic changes are, for the most part, temporary. With this, I’d like to Segway into the theme of Evolution.
ReplyDeleteThe theme of Evolution is very prominent in such a case because there is a selective advantage to being able to regulate genes for necessary proteins. If a certain gene means nothing, then a mutation where the gene doesn’t exist shouldn’t be a problem. However, since genetic material can’t just disappear, unless improper meiosis occurs in the parent cells, the useless gene would be replaced by something that is potentially more useful. This new organism would have a selective advantage over others of its own sex and would breed more efficiently to yield more beneficially mutated progeny. This increase in progeny would then contribute to the changes in the population’s gene pool. Then even more variations and mutations can occur when those with the old genome breed with those of the new genome. I believe that it is a combination of the two forms of mutation and inherited DNA changes that influence the change in the genetic pool of a species. It is, however, interesting to think about the prospect that epigenetic changes can interact with mutations in the nucleotide sequence. This would give rise to a whole new field of study: how can a gene and a possible modification for a different gene function together in the progeny of two organisms?
Article:
http://www.ncbi.nlm.nih.gov/books/NBK21276/
Jesse Pukshansky (jesse.pukshansky@gmail.com)
One should consider the type of organism and the size of a population, as well as other characteristics that make a species unique when considering the frequency or mutations and the speed of evolution. Shenk states that that the genetic mutation can be widespread in a matter of months, a short period of time compared to other species. There may be a difference between the spread of a genetic mutation based on if the species is k-selected or r-selected. Referring to Campbell, an r-selected species, like the fly, would be selecting "life history traits that maximize reproductive success in uncrowned environments (low densities)" (1185).
ReplyDeleteSome traits that are prevalent in an r-selected species would be a small body size, a short generation time, and the ability to disperse offspring widely, all of which would make sure that enough offspring pass on genes and survive to reproduce again. These traits are specific to the r-selected species, and have been favorable for the fruit fly since the organism is alive still today. Having certain mutations may also be a favorable trait, as through evolution and with enough time, a new trait could develop as necessary within the community. For example, this could be a new protein made from a mutated gene. Through time, the population has evolved and shows traits needed to survive and reproduce.
Scientists that worked on this project demonstrate interest in the variety within a few fruit fly species. The article titled, "Fruit Fly Blitz Shows the Power of Comparative Genomics" explains how 10 genomes of different fruit fly species were compared to track down the evolution of genes, and even cellular processes (http://www.sciencemag. org/content/318/5852/903.summary?sid=3669a0ec-6736-4361-9ce5-3fba4d3327ec). The fruit fly is an appropriate organism to study and analyze since it is an r-selected species and has a short generation time.
Campbell defines epigenetic inheritance as "inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence" (358). This focuses on examining changes in the chromatin, which can be reversed. At the molecular level, the chromatin modifications can be working with each other in an orderly way to provide variety in subsequent generations.
I agree with Jesse's statement that the "environment" will "force these changes", referring to the epigenetic changes. He explained the effect that different environments would have on the fly that is native to another environment. I would also argue that at the molecular level different variations would cause some mutations that could possibly produce flies that can withstand such drastic environmental changes. With thousands of years, the evolution of even a fruit fly can be broken down and analyzed for specific mutations and how these specific organisms react to different environments.
(Weronika Dudkiewicz wpd1414@gmail.com)