The Epigenetics of Identical Twins

Summary

Identical twins begin with the same DNA sequence, but their traits can diverge over time because their epigenomes change. Epigenetic tags can switch genes on or off without altering the underlying genetic code.

During fertilization, many epigenetic tags are erased, though some remain on imprinted genes. When one embryo splits into two, the twins initially share the same genome and a very similar epigenome. As their cells specialize into types such as muscle, skin, and bone, different tags help activate or silence genes, giving each cell type its own epigenetic profile.

Twins’ epigenomes tend to be similar at birth and in early life. As they grow older, environmental differences—including diet, physical activity, toxin exposure, and stress—can affect gene activity. By adulthood, these changes may produce distinct patterns of gene expression, making the twins increasingly different despite retaining the same DNA sequence.

Researchers and Sources

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