Thursday, 23 August 2012

Epigenetics: An insight into how we really work



Imagine you had a long lost twin which you were separated from at birth, you lived separate lives for 60 years and finally met up after all that time. Would they look the same as you? Be the same height and weight? The correct answer would most likely be no, you would probably not be the same height, have the same personality or have exactly the same face. Because the different lives you've lived have shaped you epigenetically and set you apart from your twin. 


Epigenetics literally means above genetics and it refers to the beacons that are on top of DNA (Craig et. al). This branch of genetic research which concerns itself with alterations to DNA expression after the individuals genetic code has been formulated, it occurs without any mutations to the genome. Environmental cues such as a shortage of food or perhaps a raise in temperature can flick a switch in the expression of some genes to counteract a sudden change in the environment. Or it may be caused by a constant exposure to something such as cigarette smoke or.  An excellent example of the process of epigenetics can be seen when observing monozygotic twins. Being monozygotic they have exactly the same genome, therefore they should exhibit exactly the same genotype and phenotype. However over the course of their lives they experience different things and take separate paths from one another, which in turn leads to the slight variation you often see between twins such as the shape of their face or height. This concept greatly affected the the sceintific communities view on disease as it appears that both nature and nurture determine the expression of disease. It is not uncommon for diseases such a Stroke, Crohns Disease, Rheumatoid Arthritis and Breast Cancer to affect one twin and not the other, giving basis to the view that ones environment is just as important as ones genetic information. The most interesting part of this whole epigenetic process is that the new traits are inheritable, so what your grandmother was doing 60 years ago may be affecting your life today.
Both these rats have exactly the same Genome

The body changes gene expression two ways, through histone proteins and methyl groups which bind onto DNA. Methyl groups and DNA go hand in hand, as the methyl groups tell the DNA what to do. All cells in the body have the same genetic code, but they all have different jobs and functions to perform and the methyl groups tell the cells what their job is. The difference between an eye cell and a red blood cell is the suppression of different sections of genetic code by methyl groups, which causes a specific expression. Histones on the other hand, act like spools which tighten or loosen the DNA strands exposing different sections so that they may be expressed. Together they can completely change gene expression and govern the cellular behavior of an individual.

A methyl group binding to DNA

Understanding how we operate epigenetically opens up so many scientific possibilities for getting exactly what we want from the genetic information we have inherited and allows possibly a non manipulative method of genetic change. This branch of research offers an incredibly in depth look at ourselves, changing our views on how the past has affects us, and shedding a new light on how what we do right now will affect those who come after us.

References:

Learn Genetics (2012), IDENTICAL TWINS: PINPOINTING ENVIRONMENTAL IMPACT ON THE EPIGENOME


Stephanie A. Tammen, Simonetta Friso, Sang-Woon Choi et al. (2012) Epigenetics: The link between nature and nurture. DOI: 10.1038/ng.2361 Viewed August 22 (2012)





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