The Facts on Human-Animal Chimeras

Q: Does the National Institutes of Health fund research on human-animal chimeras, or organisms that are part-human, part-other animal? 

A: With some exceptions, the NIH doesn’t fund research on human-animal chimeras. But the agency has proposed a rule to widen the scope of research it funds in this area.

FULL QUESTION

I’ve been seeing some news online about the ban on the development of animal/human DNA hybrids has been lifted. Is this true?

FULL ANSWER

In Greek mythology, a “chimera” is a fire-breathing creature that’s part-lion, part-goat and part-snake. Within science, the term applies to a much less fantastical organism.

According to the Merriam-Webster Medical Dictionary, created in collaboration with the NIH, a “chimera” is “an individual, organ, or part containing tissue with two or more genetically distinct populations of cells.” Normally, all the cells in an organism’s body contain the same genes. But there are exceptions.

For example, a once-pregnant woman could be considered a chimera because she can carry her baby’s cells in her body for years, if not for the rest of her life. People also can be born chimeras if two fertilized eggs fuse in early development. In both cases, a single organism is composed of cells that contain different genes.

One of our readers sent us a question about yet another kind of chimera — one made up of cells from humans and