Epigenetics, which literally means “above genetics,” layers an extra level of information on top of the DNA sequence, which on its own is only about 750 megabytes of data574 encoding 50,000 genes.575 All our dividing cells are genetically identical, carrying a full complement of our DNA, but each cell doesn’t need to express all our tens of thousands of genes. Our nerve cells don’t need to be pumping out liver enzymes, and our heart cells don’t need to be growing hair. That’s where epigenetics comes in—in effect, it’s what switches genes on and off. There are a multitude of ways our body does
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