Epigenetic processes are chemical reactions tied to neither nature nor nurture but representing what researchers have called a "third component".
表观遗传过程是一种化学反应，与天生和后天培养都没有关系，但它代表了研究人员所说的“第三种成分”。
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Other epigenetic processes appear to occur randomly, while others are normal, such as those that guide embryonic cells as they become heart, brain, or liver cells, for example.
Studies of animals, for example, have shown that when a rat experiences stress during pregnancy, it can cause epigenetic changes in a fetus that lead to behavioral problems as the rodent grows up.