All cells in your body have the same DNA, yet they express different proteins and do different things. How does that happen? Various alterations in your cells affect the expression of genes, without altering their contents. This is known as epigenetics. Cells of different tissue types have different epigenetic alterations that lead them to produce different proteins, which allows them to fill different functions.
Once a cell has chosen its job and accumulated epigenetic alterations that lead it to produce the correct proteins, those alterations usually persist through cell division. This means that if a gene is deactivated in a mother cell, it will also be deactivated in both daughter cells. This allows liver cells to stay liver cells, and kidney cells stay kidney cells.
However, as an individual ages, random errors are introduced and daughter cells stop resembling their mother cell as strongly; they may pick up new epigenetic alterations, or lose old ones. This leads to the expression of proteins inappropriate for the cell, or the loss of proteins necessary for the cell to function. Changes of this kind are known as epigenetic drift, a hallmark of aging.
Epigenetic drift contributes to a variety of diseases of aging, including cancer, Alzheimer’s
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