Epigenetic+Control+of+Gene+Expression

=Epigenetic Control of Gene Expression =


 * What is Epigenetics?**

"Epi-" is a Greek prefix that translates to "upon" or "on top of." Epigenetics is therefore, "On top of Genetics." Epigenetics attempts to explain cell differentiation and how/why genes express themselves when exposed to different environments.


 * Background**

All the cells in our bodies contain the same fundamental DNA code. This code is responsible for determining who we are, the way we look and how our body functions. For a cell to distinguish itself among others, it must express only specific parts of the DNA code while muting others. For example, a liver cell and a skin cell contain the same exact DNA code contained in their chromosomes. The big difference is the proteins that DNA is actively coding for. This leads to differentiation of cells and is why eukaryotes like ourselves exist. Not only are internal factors responsible for the way genes express themselves, outside factors can play a role in gene expression as well. The environment we live in and our everyday lifestyles can cause changes in which genes are being actively expressed. "Cancer Epigenetics for the 21st Century: What's Next?" states that methylation of cancer cells can silence the cells and stop them from replicating [1]. So essentially, the methylation of cancer cells mutes the genes and stops them from undergoing rapid replication. In 1962, John Gurdon removed the nucleus of a fertilized frog egg and inserted the nucleus of a frogs skin cell in its place. The cell eventually developed to be an entirely new frog (with the same DNA), a clone. Gurdon proved that mature, specialized cells contain the DNA necessary to form all the specialized cells found in a mature frog. Thus proving that DNA does not vanish in specialized cells and that they only express needed genes. Epigenetics allows us to really question how hard-wired our own DNA is, and how specific it is in our everyday lives. Is it possible to turn genes on and off with a "flick" or a switch? This may explain why identical twins raised in different environments may not appear identical even though their DNA is exactly the same. Other questions include the possibility that if one day, parents will have the power to "Build a Baby." Epigenetics suggests that our DNA is relatively permanent, however how it is expressed is not.

Figure 1. John Gurdon's experiment with differentiated cells


 * Epigenetics and its Ability to Cross Generations is not Completely Understood**

Specific mechanisms involved in how epigenetic traits are carried across generations is not totally clear. One study states, " Epigenetic mechanisms can stably alter transcriptional activities and those can be transmitted through mitoses and sometimes also meiosis. Therefore, they can be propagated across generations as alternative epigenetic states of genes, so-called epialleles."[2] Another experiment tries to determine the influence of exposure to heavy metals and other toxins on the DNA of humans. The article states, "arsenic exposure leads to gene-specific DNA hypermethylation in human subjects."[3] These changes can lead to susceptibility to disease and various other heritable developmental abnormalities due to methylation blocking the transcription of specific genes.


 * Current Research**

-Stem cell research -Tumor supression -Cancer predisposition and other related research -Methylation -Cloning -How lifestyles influence gene expression


 * Conclusion**

Pending further research, epigenetics has potential to be a serious science in our everyday lives. It is known that gene expression is not permanent and the ability to control it is somewhat of moral dilemma. However, the ability to repress cancer or detect potentially fatal diseases and eliminate them is very lucrative. In the future, it must be determined which practices of gene control are moral, practical and applicable.

**References** code [1] Esteller M. Cancer Epigenetics for the 21st Century: What's Next? (2011) //Genes and Cancer,// 2 (6),                pp.604-606

[2] Jerzy Paszkowski, Ueli Grossniklaus, Selected aspects of transgenerational epigenetic inheritance and            resetting in plants, Current Opinion in Plant Biology, Volume 14, Issue 2, April 2011, Pages 195-203

[3] Martinez-Zamudio R, Ha HC. Environmental Epigenetics in Metal Exposure. Epigenetics 2011; 6:820-827. code