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Mechanisms of Cellular Epigenetic Inheritance

Epigenetic inheritance is basically the observation that offspring may inherit altered traits due to its parents past experiences. So a parents experiences, in the form of epigenetic tags, can be passed down to future generations. Epigenetic inheritance systems are  the processes and mechanisms that underlie cellular inheritance.  There are four types of EISs recognized today and they are....

  1. EIS based on self sustaining regulatory loops
  2. EIS based on three-dimensional templating
  3. Chromatin marking EIS
  4. RNA mediated EIS

All of these can contribute to between-generation epigenetic inheritance.

SELF SUSTAINING LOOPS: These are metabolic circuits through which different patterns of activity can be maintained resulting in alternative heritable phenotypes. The early studies of the loops involved the bistability of the lac operon of Escherchia coli and this system has been analyzed at molecular and theoretical levels. The studies showed that when inducer concentrations are low, genetically identical cells can generate two alternative, true breeding, stable phenotypes. These loops have been described in bacteria and other taxa.

Three-Dimensional Templating: Structural inheritance refers to the inheritance of alternative three dimensional structures through spatial templating: a variant 3-D structure in a mother cell guides the formation of a similar structure for a daughter cell, leading to the transmission of the architectural variant. - This all started from the investigation of cortical variations in ciliates. A modified organization of the cilia on Paramecium can be inherited through many asexual and sexual generations. Another form of this structural inheritance is the propagation of prions. A single protein can misfold into several different conformations that have specific growth dynamics, stabilities, pathologies, and cross species infectivity. Many prions can interact which could lead to the formation of different transmissible phenotypes. SO unicellular organisms which have the same genotype and live in the same enviroment can exhibit heritably different morphologies and physiologies.

CHROMATIN MARKING EIS:  Chromatin is what is inside chromosomes and includes DNA and everything in it. The organization and location of chromatin and chromosomes determine everything concerning how genes are transcribed, how DNA repair works, how different chromosomal domains are organized, and how chromosomes behave during the cell cycle. There is evidence that chromatin variations can be transmitted through generations of people. Therefor the study of the chromatin marking EIS is crucial for the understanding of development and heredity.

RNA MEDIATED EIS: RNA is central to the regulation of cellular dynamics in the eukaryotes and is also involved in cell and organism heredity. RNA interference has been located in all eukaryote phyla from yeast to man. In RNA pathways, double stranded RNA molecules are chopped into shorter dsRNAs by the enzyme dicer. The resulting siRNA is loaded onto a complex of proteins, one strand of the duplex is removed and the other directs silencing. RNA can affect cell and organism heredity in several different ways, one example being the result of replication of siRNA through RNA dependent RNA polymerase.

5 thoughts on “Epigenetics…Epige-what-ics?

  1. rebeccaleon

    After reading both of the articles for this week on epigenetic inheritance it is apparent that the authors are trying to convey the importance for trying to reduce the negative effects that our environment has on epigenetic inheritance. With how complex our society is today and the numerous factors that go into effecting epigenetic inheritance is it even possible to make a significant difference in this ongoing problem? I think it is definitely possible to make small scale progress through public education. Maybe it is possible to make a larger impact on how our environment influences our epigenetics through government reform (e.g., making it illegal to make and distribute water bottles with BPA).

    So, are we seeing this research leading to positive changes in our environment o ris it just making us more aware of the problem? Could it be too early in the research process on epigenetics for change to occur?

  2. Meghan Steel

    I understand the implications of epigenetic research and I understand, for the most part, some of the methods of the pseudo-inheritance. The one thing I don't understand, however, relates mainly to the three-dimensional templating. Can this type of epigenetic inheritance only be passed through the offspring from the maternal standpoint? Is the environment in which the mother grew up and lived more important than that of the father?

  3. Jonathan Belanich

    It seems clear by amount of research being conducted in that involves epigenetics, that it is becoming a large focus of genetics. We only have a relatively few examples of epigenetic inheritance, as compared to genetic inheritance, but it already has the power to explain some methods of inheritance that we cannot figure out.

    I would like to know which of the four epigenetic inheritance systems mentioned, is the primary method of inheritance. By just reading the descriptions, I would say the the Self Sustaining Loops are the probable factor.

  4. Emily Barron

    One interesting thing I read in the article was that not all prions are bad. I've never heard about good prions, so the word has always been associated with having deleterious effects. The article said only RNA mediated and chromatin marking EIS has been shown to be inheritable through sperm or egg. I think it would be interesting to research how and if the other can be inherited.

  5. Brittany Fuller

    There is a lot of research being done on this topic it seems like. We will probably learn more about the topic in the next several years. I think that epegenetic inheritance is an interesting topic.

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