Table 1.
Examples of definitions involving epigenetics, ignoring usage prior to Waddington, illustrating how they have changed across the years. All are direct quotations from the original sources (including quotation marks used there), with one exception as indicated. The various definitions also illustrate continuing variation, especially with respect to the breadth of the definition and also whether some degree of inheritance is necessarily implied. Epigenetic effects are one mechanism of early-life effects, the more general topic covered in this paper.
| Author(s) | Year | Definition |
|---|---|---|
| Waddington | 1939 | One might say that the set of organizers and organizing relations to which a certain piece of tissue will be subject during development make up its “epigenetic constitution” or “epigenotype.” |
| Waddington | 1942 | the processes involved in the mechanism by which the genes of the genotype bring about phenotypic effects |
| Holliday | 1987 | concerned with the strategy of genes in unfolding the genetic program in development |
| Atchley and Hall | 1991 | we use the term ‘epigenetic factors’ for those factors that arise external to a developing cell and influence the cell’s DNA extrinsically |
| Riggs et al. | 1996 | The study of mitotically and/or meiotically heritable changes in gene function that cannot be explained by changes in DNA sequence |
| Wu and Morris | 2001 | the study of changes in gene function that are mitotically and/or meiotically heritable and that do not entail a change in DNA sequence |
| Jaenisch and Bird | 2003 | Many [alterations] in gene expression arise during development and are subsequently retained through mitosis. Stable alterations of this kind are said to be “epigenetic,” because they are heritable in the short term but do not involve mutations of the DNA itself. |
| Holliday | 2006 | the study of nuclear inheritance which is not based on changes in DNA sequence |
| Bird | 2007 | the structural adaptation of chromosomal regions so as to register, signal, or perpetuate altered activity states |
| Jablonka | 2009 | the study of the processes that underlie developmental plasticity and canalization and that bring about persistent developmental effects in both prokaryotes and eukaryotes |
| Jablonka and Raz | 2009 | Epigenetics is the study of the processes that underlie developmental plasticity and canalization and that bring about persistent developmental effects in both prokaryotes and eukaryotes. |
| Jablonka and Raz | 2009 | Epigenetic inheritance is a component of epigenetics. It occurs when phenotypic variations that do not stem from variations in DNA base sequences are transmitted to subsequent generations of cells or organisms. |
| Halfmann and Lindquist | 2010 | encompasses all mechanisms for the inheritance of biological traits that do not involve alterations of the coding sequence of DNA |
| Jablonka | 2013 | The molecular processes that underlie persistent developmental changes are known as epigenetic mechanisms. |
| Tammen et al. | 2013 | Epigenetics is the field of study surrounding stable alterations to the DNA and histone proteins that alter gene expression (Jaenisch and Bird, 2003). |
| Laland et al. | 2014 | Paraphrase: Emerging evolutionary synthesis includes epigenetics among other kinds of extra-genetic inheritance. |
| Waterland | 2014 | Epigenetics is the study of mitotically heritable alterations in gene expression potential that occur without alterations in DNA sequence (Jaenisch and Bird, 2003). |
| Pluess | 2015 | study of changes in organisms caused by modification of gene expression rather than alteration of the DNA |