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Such redefinitions however are not universally accepted and are still subject to dispute.
The NIH "Roadmap Epigenomics Project", ongoing as of 2016, uses the following definition: "For purposes of this program, epigenetics refers to both heritable changes in gene activity and expression (in the progeny of cells or of individuals) and also stable, long-term alterations in the transcriptional potential of a cell that are not necessarily heritable." In 2008, a consensus definition of the epigenetic trait, "stably heritable phenotype resulting from changes in a chromosome without alterations in the DNA sequence", was made at a Cold Spring Harbor meeting.
This view encompasses all of the possible developing factors on an organism and how they not only influence the organism and each other, but how the organism also influences its own development.
The developmental psychologist Erik Erikson wrote of an epigenetic principle in his book Identity: Youth and Crisis (1968), encompassing the notion that we develop through an unfolding of our personality in predetermined stages, and that our environment and surrounding culture influence how we progress through these stages.
It is, as defined by Arthur Riggs and colleagues, "the study of mitotically and/or meiotically heritable changes in gene function that cannot be explained by changes in DNA sequence." The term "epigenetics", however, has been used to describe processes which have not been demonstrated to be heritable such as some forms of histone modification; there are therefore attempts to redefine it in broader terms that would avoid the constraints of requiring heritability.
The more recent usage of the word in science has a stricter definition.
The phrase "genetic code" has also been adapted—the "epigenetic code" has been used to describe the set of epigenetic features that create different phenotypes in different cells.
Taken to its extreme, the "epigenetic code" could represent the total state of the cell, with the position of each molecule accounted for in an epigenomic map, a diagrammatic representation of the gene expression, DNA methylation and histone modification status of a particular genomic region.
More typically, the term is used in reference to systematic efforts to measure specific, relevant forms of epigenetic information such as the histone code or DNA methylation patterns.
Due to the early stages of epigenetics as a science and the sensationalism surrounding it in the public media, David Gorski and geneticist Adam Rutherford advised caution against proliferation of false and pseudoscientific conclusions by new age authors who make unfounded suggestions that a person's genes and health can be manipulated by mind control.