Epigentics: The "Glitch" in the Program Mendel Never New

What is epigenetics? Why is it important? The term epigenetics was first coined by Conrad Waddington in 1939 to define the unfolding of the genetic program during development. In addition, he coined the term epigenotype to define "the total developmental system consisting of interrelated developmental pathways through which the adult form of an organism is realized". Today the term epigenetics is used to define the mechanism by which changes in the pattern of inherited gene expression occur in the absence of alterations or changes in the nucleotide composition of a given gene. A literal interpretation is that epigenetics mean "in addition to changes in genome sequence." In other words the observed phenotype is the result of colective changes "on" the genes not due to changes "in" the genes. Several different types of epigenetic events have been identified. DNA methylation is likely to be the most important epigenetic event controlling and importantly maintaining the pattern of gene expression during development. Other DNA modification events are also known to effect epigenetic phenomena including acetylation, methylation phosphorylation, ubiquitylation and sumoylation of histone proteins. Thus, it should be clear that the same events that affect chromatin structure can be defined as epigenetic events.

As to the second question, why is epigenetics important? The importance of epigenetics is that an individual can manifest a disease or syndrome without ever having inherited a defective gene from either parent or having sustained a mutational event in a gene(s) after birth due to the suns rays or to other forms of ionizing radiation (e.g. gamma rays). In addition, ones exposure to environmental toxins, chemical DNA modifying compounds, etc. can effect changes in the epigenome resulting in altered patterns of gene expression that may manifest with untoward symptoms.

I will refer to this post in future posts attesting to the consequences of an altered epigenome.


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