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How is an embryo created through somatic cell nuclear transfer?

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Replica of a woolly mammoth with long curved tusks and shaggy fur on display in a museum exhibit, set against a dramatic painted landscape backdrop. — de-extinction The woolly mammoth (*Mammuthus primigenius*)—represented here by a replica in a Canadian museum—is an example of an extinct species that someday could be resurrected through de-extinction.

Somatic cell nuclear transfer (SCNT) is a technique used to create an embryo by transferring the nucleus from a somatic (body) cell of the target animal into an enucleated donor egg—an egg cell from which the original nucleus has been removed.12

Once the somatic nucleus is inside the egg, the egg's cytoplasm contains factors that reprogram the nucleus to function as a zygote nucleus. The egg is then stimulated in a laboratory setting to initiate cell division, which results in the formation of an embryo. In the context of de-extinction, this reconstructed embryo is typically transplanted into the uterus of a surrogate mother from a closely related species to develop.12

While this process is a key tool for potential species resurrection, it remains technically challenging and raises significant ethical questions regarding the welfare of cloned individuals and the broader implications of altering natural history.2