Credit: Chris Buzelli

This spring, news of a biological breakthrough arrived in the form of baby marmosets whose feet glowed green under ultraviolet light. Researchers at the Central Institute for Experimental Animals in Kawasaki, Japan, had genetically engineered the monkeys to incorporate a gene, derived from jellyfish, that produces green fluorescent protein. It was the first time scientists had added a gene to a primate in such a way that a new trait could be passed to a second generation.

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