A chimera is an organism that is made up of a mixture of genetically different cells that have come from different zygotes. This can be from the merger of two non-identical twins zygotes, for example. Scientists have moved on from mice and rats to see how stem cells behave when they are within a primate:
This study is useful to see how stem cells inserted in live animals behave, rather than just viewing their growth in the lab. This has implications for future stem cell work in humans as the monkeys are more closely related to humans than other animals. But animal rights groups donot like this approach as they believe it raises ethical questions about the welfare of the animals involved. What do you think?