Epigenetic landscape is a metaphor for biological development. Its originator, Conrad Hal Waddington, said that cell fates were established in development much like a marble rolls down to the point of lowest local elevation. Waddington suggested visualising increasing irreversibility of cell type differentiation as ridges rising between the valleys where the marbles (cells) are travelling.
Today, the term refers to the combined epigenetic modifications of a given domain of DNA sequence. Epigenetic modifications include methylation of cytosine residues of DNA and post-translational modifications of the histone proteins associated with the DNA strand. The specific combination of epigenetic modifications determines the conformation of the chromatin fibre into which the DNA and histones are packaged, and can thereby regulate the transcriptional potential of the underlying genes.
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