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The word “epigenetics” once meant simply “development”—that is, the way the genome worked itself into an organism through the production and regulation of proteins and absorption of food and materials from the outside, and the turning of some genes on and others off in different tissues.  Now, however, the term means roughly “forms of inheritance that rest on modification of the DNA sequence,” and by “DNA sequence” I mean the sequence of four bases (A, G, C, and T) that constitutes the DNA code.