The DNA contained within each of our cells is exactly the same, yet different types of cells - skin cells, heart cells, brain cells – perform very different functions. The ultimate fate of these cells is encoded not just in the DNA, but in a specific pattern of chemical modifications that overlay the DNA structure. These modifications, or epigenetic markers as they are called, are stably carried in our genomes — except for at times when the cells change their fate, such as what occurs when the sperm meets the egg. Then they are erased completely.
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