A brief categorization of contemporary definitions of epigenetics
| Epigenetics definition | Focus of definition | Interpretation | Representative reference |
| Regulation of gene expression | Mechanistic view of the epigenome | • Uses the literal etymology of ‘above’ or ‘beyond’ genetics | Shukla et al., 2009 |
| • No particular focus on transgenerational transfer | |||
| Stable changes in gene function without changes in DNA sequence | Gene function | • Narrows definition of epigenetics to consider modification of chromatin | Griesemer, 2002; Bird, 2007 |
| • No particular focus on transgenerational transfer | |||
| Non-genetic causes of a phenotype | Phenotype | • Focuses on linkage of mechanism to outcome (phenotype) | Wolf et al., 2008; Gilbert and Epel, 2009; Krause et al., 2009 |
| • Transgenerational transfer is part of a larger suite of outcomes, including developmental plasticity | |||
| Study of heritable changes in gene function that occur without a change in the DNA sequence | Transgenerational transfer of gene function | • Explicit focus on transgenerational transfer (inheritance) of gene function | Kiefer, 2007; Lemos et al., 2008; Lopez et al., 2009 |
| • Focuses on mechanism with lesser focus on phenotypic outcome or evolutionary implications | |||
| Study of heritable phenotype without a change in the DNA sequence | Transgenerational transfer of phenotype | • Explicit focus on transgenerational transfer (inheritance) | Groothuis and Schwabl, 2008; Youngson and Whitelaw, 2008 |
| • Focuses on phenotypic outcome and evolutionary implications, with minor focus on mechanism | |||
| Study of processes that give rise to developmental plasticity and canalization | Persistent phenotype as a result of events that occur during development | • Distinction among ‘epigenetics’, ‘epigenetic inheritance’ and ‘cellular epigenetic inheritance’ | Jablonka and Lamb, 2005; Jablonka and Raz, 2009 |
| • Focuses on cellular phenotypic outcome and evolutionary implications, with major focus on mechanism | |||
| • Focuses on transgenerational transfer via gametic transmission | |||
| Alteration of gene expression by modification of chromatin | Strict inheritance of epigenetic marks such as imprinted genes | • Focuses on the overlap between transgenerational non-genomic transgenerational inheritance and epigenetic inheritance | Gluckman et al., 2007 |
| • Distinction between indirect and direct epigenetic inheritance |
| Epigenetics definition | Focus of definition | Interpretation | Representative reference |
| Regulation of gene expression | Mechanistic view of the epigenome | • Uses the literal etymology of ‘above’ or ‘beyond’ genetics | Shukla et al., 2009 |
| • No particular focus on transgenerational transfer | |||
| Stable changes in gene function without changes in DNA sequence | Gene function | • Narrows definition of epigenetics to consider modification of chromatin | Griesemer, 2002; Bird, 2007 |
| • No particular focus on transgenerational transfer | |||
| Non-genetic causes of a phenotype | Phenotype | • Focuses on linkage of mechanism to outcome (phenotype) | Wolf et al., 2008; Gilbert and Epel, 2009; Krause et al., 2009 |
| • Transgenerational transfer is part of a larger suite of outcomes, including developmental plasticity | |||
| Study of heritable changes in gene function that occur without a change in the DNA sequence | Transgenerational transfer of gene function | • Explicit focus on transgenerational transfer (inheritance) of gene function | Kiefer, 2007; Lemos et al., 2008; Lopez et al., 2009 |
| • Focuses on mechanism with lesser focus on phenotypic outcome or evolutionary implications | |||
| Study of heritable phenotype without a change in the DNA sequence | Transgenerational transfer of phenotype | • Explicit focus on transgenerational transfer (inheritance) | Groothuis and Schwabl, 2008; Youngson and Whitelaw, 2008 |
| • Focuses on phenotypic outcome and evolutionary implications, with minor focus on mechanism | |||
| Study of processes that give rise to developmental plasticity and canalization | Persistent phenotype as a result of events that occur during development | • Distinction among ‘epigenetics’, ‘epigenetic inheritance’ and ‘cellular epigenetic inheritance’ | Jablonka and Lamb, 2005; Jablonka and Raz, 2009 |
| • Focuses on cellular phenotypic outcome and evolutionary implications, with major focus on mechanism | |||
| • Focuses on transgenerational transfer via gametic transmission | |||
| Alteration of gene expression by modification of chromatin | Strict inheritance of epigenetic marks such as imprinted genes | • Focuses on the overlap between transgenerational non-genomic transgenerational inheritance and epigenetic inheritance | Gluckman et al., 2007 |
| • Distinction between indirect and direct epigenetic inheritance |