Topics: Gene expression, DNA, Epigenetics Pages: 5 (1536 words) Published: February 6, 2013
Initially, when scientists were beginning to grasp the concept of DNA and its storage genes, they believed certain genes present in the DNA sequence would be expressed and those who were not originally expressed would remain hidden throughout that organisms’ lifetime. The discovery of epigenetics challenged that. Scientists have now discovered there are certain genes that are present in the DNA sequence that at first, are not being expressed but then, by other mechanisms, are “turned on”. This discovery was a breakthrough in science because it brought along the possibility of manipulating genes to suppress the undesired genes and display those that could be beneficial. If our society is successful in understanding what exterior mechanisms could turn a gene “on” or “off”, we could potentially live healthier lifestyles, giving us control over our gene manifestation. This study of heritable changes in the DNA was named epigenetics because of “epi” is the Greek root meaning above, over, or outer. C.H. Waddington coined this term in 1942. He was the first attempt to describe the differential of cells from there initial state in embryonic development. Not to be mistaken for a mutation, epigenetics does not tamper DNA sequence but rather modify the activation of certain genes. Epigenetic changes are preserved when cells divide. Most epigenetic changes only occur within the course of one individual organism's lifetime, but, if gene deactivation occurs in a sperm or egg cell that results in fertilization, then some epigenetic changes can be transferred to the next generation. This is where hereditary factors take role. How genes might interact with their surroundings is surely important when it comes to producing a phenotype. One experiment that supports this statement is the shape of Combs on Chickens. In the first decade of the twentieth century, British geneticists William Bateson and R. C. Punnett conducted research showing that the shape of the comb in chickens was caused by the interaction between two different genes. Altering a gene’s surroundings is what contributes to the act of epistasis, the phenomenon where the effects of one gene are modified by one or several other genes. One known mechanism that directly affects “epi” genes is DNA Methylation. DNA Methylation is one of the several epigenetic mechanism that cells use to control gene expression. Other mechanisms include RNA Transcript differations, Prions, and Histone Methylation. DNA Methylation, specifically, is a common epigenetic signaling tool that cells use to lock genes in the “off” position. Scientists have discovered that DNA Methylation plays a huge role in genomic imprinting, development, the X- chromosome inactivation, and even the preservation of chromosome stability. For many years, methylation was believed to play a crucial role in repressing gene expression, perhaps by blocking the promoters at which activating transcription factors should bind. Presently, the exact role of methylation in gene expression is unknown, but it appears that proper DNA methylation is essential for cell differentiation and embryonic development. Moreover, in some cases, methylation has observed to play a role in mediating gene expression. Evidence of this has been found in studies that show that methylation near gene promoters varies considerably depending on cell type, with more methylation of promoters correlating with low or no transcription. Histone Methylation, often confused with DNA Methylation, involves more of the modification of certain amino acids in a histone protein by the addition of one, two, or three methyl groups. Organisms require an appropriate balance of stability and reversibility in gene expression programs to maintain cell identity or to enable responses to stimuli. Epigenetic regulation is integral to this dynamic control. Post-translational modification of histones by methylation is an important and widespread type of...

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