Epigenetics refers to changes in gene expression that are not caused by changes in DNA, but rather by environmental factors altering the phenotypes and activity of genes. This article looks into two main ways environmental changes can cause harm to humans; these are DNA methylation and Histone Modification.
De-methylation of genes can cause chromosomal instability, loss of imprinting and activation of transposable elements. Without methylation there are many opportunities for deletion of genes, silencing of genes and proteins, and instability of chromosomes, all of which create susceptibility to disruption in normal cellular activity in development or adult life. These disruptions can lead to tumours, developmental syndromes such as Angleman Syndrome and autoimmune disorders. The environment plays a role in this because organisms have the ability to adapt to their environment and when an adaptation occurs in the area of epigenetics the above conditions can result. This mainly occurs when the original factor causing adaptation is then removed from the environment but the adaptation stays.
Histone Modification has only recently been linked to health and epigenetic changes and so research has not shown all the ways in which histone modification can be harmful. Histones have many different modifications which each are responsible for different events in the areas of DNA replication, repair and condensation as well as embryo development and activating and repressing certain genes and proteins. Histones can sometimes silence genes that are needed for health such as tumour suppressing genes. This can be done with relation to the environment since the environment often signals the histones to activate or suppress genes and proteins. However sometimes feedback loops between environmental stimulus and cells can result in wrongly activation or suppressing certain genes.
So therefore our environment, including such things as weight, the drugs we take, our hertiable gene history, can alter our gene expressions without altering our DNA and this can sometimes lead to disease.
Hurst, M. & Marra, M.A. 2009. “Epigenetics and human disease”. The Internal Journal of Biochemistry and Cell Biology, 41, p136-146
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