Figure 1.

Lamarckian aspects of epigenetic adaptation. An active regulatory gene responds to environmental stress (1) by changing its expression profile to inactive (2), which is mediated by an epigenetic change—methylation of cytosine to 5-methylcytosine. This change increases the mutation potential of the affected genome region. The longer the gene stays inactive and methylated, the higher the chance for a mutation of 5-methylcytosine to thymine, possibly accompanied by the loss of gene function (3). According to this model, long-term adaptation to an environmental influence can be permanently recorded in the genome. The described directed shaping of stably inherited traits by an environmental influence and the accompanying adaptation is a distinctly Lamarckian concept.