Editing Transgenerational Epigenetic Inheritance (section)

== 3. Intergenerational vs. Transgenerational Inheritance ==

In mammalian research, strict criteria must be met to prove ''transgenerational'' inheritance, as opposed to direct ''intergenerational'' exposure:

* '''Intergenerational (Direct Exposure):''' If a pregnant female (the F0 generation) is exposed to a toxin, the fetus (F1) is also directly exposed. Furthermore, the developing germ cells inside that fetus (which will become the F2 generation) are also directly exposed. Therefore, an altered phenotype in the F1 or F2 generation could simply be the result of direct toxicity, not true inheritance.
* '''Transgenerational (Unexposed):''' True transgenerational inheritance via a female lineage can only be confirmed if the altered phenotype persists into the '''F3 generation'''—the first generation to never be directly exposed to the original trigger. (If the exposure is through the F0 male, the F2 generation is the first unexposed generation).