Epigenetic research addresses the alterations to the chromatin template that collectively establishes and propagates different patterns of transcription or gene expression and silencing from the same genome.
The major components of chromatin are DNA and histone proteins. Two copies of each histone core protein (H2A, H2B, H3 & H4) are assembled into an octamer that has 145- 147 base pairs of DNA wrapped around it to form a nucleosome core. The nucleosome controls the accessibility of DNA to the transcription machinery and chromatin remodelling factors (Luger et al. 1997).