Epigenetics is the idea that, contrary to decades of genetic theory, your genetic code isn’t the only thing that controls how your cells behave. Scientists now realize that chemicals and other environmental influences that can modify the physical structure of your DNA are at least as important as the actual genetic code. Even more surprising, these modifications are inheritable. It’s possible, for example, that your grandmother’s poor diet could affect your own health by making your DNA harder to read for the proteins that help maintain cellular functions.

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