Epigenetics: A Historical Overview

In the first half of the twentieth century, developmental biology and genetics were separate disciplines. The word epigenetics was coined by Waddington to link the two fields. Epigenetics could be broadly defined as the sum of all those mechanisms necessary for the unfolding of the genetic programme for development. Several decades later specific mechanisms were proposed in which information was superimposed on DNA sequences. In particular, it was suggested that 5-methyl cytosine had a role in controlling gene expression, and also that the pattern of methylation was heritable. These predictions are now supported by a large body of evidence which shows that methylation is strongly associated with gene silencing…