Epigenetic Mechanisms

Abstract

While phenotypic variation such as disease vulnerability has traditionally been viewed as being determined by the interaction between genes and the environment, it is now clear that this is over-simplistic. Developmental plasticity describes the phenomenon whereby development of the phenotype from a given genotype is influenced by developmental experiences, and phenotypic variation in turn influences how the individual interacts with its mature environment, thus affecting disease risk. It is now recognized that developmental plasticity is underpinned by epigenetic processes, which are environmentally-induced changes in the patterns and regulation of gene expression brought about by a set of modifications in DNA and DNA-associated molecules, without changes in the base sequence. Epigenetic processes are phylogenetically old, and the mechanisms involved modulate both gene dosage and the conditions under which genes are expressed. Developmental plasticity is but one of several processes which are effectuated by epigenetic mechanisms; in mammals other processes include transposon silencing, cell differentiation, X-inactivation in females and genomic imprinting.