Research Information System
in: Epigenetics: Mechanisms and Clinical Perspectives, Yıldız Dinçer, Editor, Nova Science Publishers, New York, pp.15-31, 2016
The
term epigenetics was first coined by C.H Waddington in 1942, a word derived
from epigenesis and genetics. Epigenesis is the word for describing live
organisms differentiating from a single cell into an organ or organism. Epigenetic
mechanisms modulate gene expression patterns without affecting the deoxyribonucleic
acid (DNA) sequence. To stop confusions, a consensus definition was put on use of
the epigenetic trait: "stably heritable phenotype resulting from changes
in a chromosome without alterations in the DNA sequence" (1). These
mechanisms are acquired throughout life and depend on environmental clues such
as diet, lifestyle and toxin exposure. They are
heritable mechanisms so epigenetic changes can
be transferred to the new cell when cells are divided with mitosis. If this
process takes place in germ cells and meiosis, genomic imprinting may occur. In
some occasions, such as differentiation of embryonic stem cells to specific
tissues, the expression is stabilized so that the cells cannot go back to their
previous state. Although all cells in one individual have the same DNA
sequence, epigenetic regulation occurs at the specific gene loci in the
specific cells to yield specific cellular phenotypes. A change in the phenotype
does not usually effect the genotype. Gene expression can be activated or
silenced via epigenetic regulations. Epigenetic changes can alter
transcriptional activity of genes, and may mediate the differences in risk for
certain diseases. Methylation, phosphorylation, acetylation, ubiquitination,
sumoylation are included in epigenetic processes.