Fig. 1

Distinction between intergenerational and transgenerational inheritance in mammals. In the case of intergenerational inheritance, parental exposures directly influence not only embryos and/or fetuses (F1 generation), but also already developing germ cells, giving rise to the F2 generation. Thus, F1 and F2 phenotypes may be directly exposed to external developmental cues, and F3 generation is the first one where the phenotype is not through primary triggering exposure. Therefore, true transgenerational effects include those that persist into the F3 generation [8]