Thursday, April 1, 2010

Epigenes versus Genes

Coyne discusses the evolution’s impact on genes, calling them “vestigial genes” and “pseudogenes” because they are silenced after the organisms with the selective advantage to have them off survive (66-73). However, in class, we briefly discussed the effects of epigenes on a few generations in a family of organisms. Briefly discuss a few common examples of epigenes on organisms’ selective advantages. To what extent do epigenes influence microevolution and evolution over a long period of time? Finally, how do you think recent developments in the field of epigenetics may influence pseudogenes, genes, and evolution? Provide examples of such developments.


  1. Epigenes are inherited changes in a phenotype due to not DNA sequences but other forces. Such examples of the epigenes are DNA methylation and chromatin remodeling. These two processes mess with the transcription of the DNA, allowing it not to be expressed nor translated to become a protein. A selective advantage of epigenes might be that in a dire environmental situations, the cells may need more energy in producing ATP in the mitochondria. However, if the energy is wasted in transcription and translation of the protein, then the ATP production level will not rise to the occasion. However, with the epigenes, there may be changes in the readings of the DNA and production of proteins that helps organisms to survive. These epigenes affect the microevolution and evolution over a long period of time because these epigenes also have a possible change of mutation. Even though the genes themselves do not mutate, the mutations of these epigenes may result in underproduction or overproduction of a certain protein. Therefore, when such mutation gives rise to an selective advantage, then the organism can survive and reproduce more efficiently than other organisms. The development in the epigenetics may influence the pseudogenes and genes of the evolution because the epigenetic is a recently discovered part of the DNA. Previously, humans only thought that DNA is what governs the production of proteins in a body. However, with the epigenes, there might be a chance of finding an organism with a mutation of only the epigenes that gave rise to the branching off of the species.

    Jerry Coyne: Why Evolution is True

    Niel Campbell and Jane Reece: Biology: AP Edition 8e

  2. A psuedogene is a gene that does not function- it doesn't make functional protein. Such genes are often turned off due to a mutation causing an evolutionary advantage, such as energy consercation. This is seen in GLO. GLO produces enzymes used to make vitamin C. In many organisms (like humans) this is psuedo GLO because it is inactive; humans do not need to make their own vitamin C because we get enough of it in our diets. Having this gene inactivated saves us from spending that extra energy making vitamin C. This contributes to the idea of change within a kind (microevolution): A species that used to produce vitamin C now does not- that is a change but the species is still the same species. If a mutation caused a greater change, that could lead to the transformation of species. New developments in epigenetics may alter the natural progression of evolution. A main area epigenetics is used in would be cancer treatments. People with cancer are sometimes treated by having certain genes turned on or off to stunt that cancerous growth. So genes that were previously inactive are still available to use to benefit organisms even if evoltuionary trends have shown it is not necessary for survival. Evolution is disrupted because we can now control which genes are considered "necessary."

    sources: Why Evolution is True, Jerry Coyne

  3. Epigenetics – a different type of inheritance – delves into the changes in gene function not related to changes in the DNA sequence. Therefore, epigenetics does not deal with the “inheritance of mutational changes” but rather of several independent roots, one being the environment. Besides DNA methylation that liondrummer mentioned, the molecular basis of epigenetics also has to do with the Polycomb/Trithorax systems (first found in the fruitfly Drosophila m.). This system acts to maintain repressed or active transcription states of genes; the systems essentially memorize the gene-expression patterns and that silencing of specific genes may be transmitted between fruitfly generations. Alterations in the Polycomb/Trithorax systems or in DNA methylation may be inherited by subsequent generations, for example: the silencing of the gene Lcyc that controls flower symmetry or the mouse locus that regulates coat color. The parents may be genetically identical, but different epigenetic states cause the offspring to have different coat colors.
    The science of epigenetics is revolutionary because essentially, the environment may have an effect on generation after generation of organisms. Studies have shown that the environment and ageing are linked to epigenetic effects on phenotype. One example is monozygotic twins (that originally exemplified genetics at work regardless of environmental pressures); monozygotic twins do not always have the same disease susceptibility – older twins differ substantially in the different amounts of DNA methylation; therefore, besides epigenetics used in cancer treatments said by Stephanie K., the mother’s behavior may effect the chemistry of the DNA in her offspring. Therefore, epigenetics in this sense creates a selective advantage for organisms if maternal care and nurturing relates to the altering of DNA methylation.
    In response to evolution arising partly from mutations, epigenetics does not play a role. Rather, epigenetic processes are buffers of genetic variation. According to Nature (May 2007), epigenetic marks are responsive rather than proactive; it does not initiate the change but registers the change that events such as a switch in gene expression have been imposed. Without epigenetic mechanisms, changes in gene-programming may be lost, DNA damage may not be repaired, and disruptions in chromosome organization may go unrecognized.
    According to TIME (Why Your DNA Isn’t Your Destiny by John Cloud), nurture acts on genes and creates a “short-circuit evolution” that refutes the idea that natural selection acts evolution over millions of years. In a single generation, environmental conditions such as starvation may leave a mark on the genetic material in eggs and sperm (studies in northern Sweden). Therefore, lifestyle choices have an effect on the expression of genes resulting from epigenetic studies; but scientists are developing drugs that may silence “bad” genes and jump-start “good” genes.
    In this manner, epigenetics influence pseudogenes: apart from the pseudogene GLO stated by Stephanie K., the OR gene related to our sense of smell is also “dead” (Coyne 70). Such inactive genes do underscore the relationship between evolution and gene regulation over time; but epigenetics underlines a different type of evolution that deals with choices.


    Jerry Coyne: Why Evolution is True

    Proquest article:

    Campbell Biology textbook

    Article in class: Why your DNA isn’t your destiny (John Cloud)