Chimeras

Chimeras or chimera in common usage refers to beings that combine features from different origins. In Greek mythology, the Chimera is a fire-breathing monster typically described as a hybrid of a lion, a goat, and a serpent. The term has since broadened to describe any composite organism or structure.

In biology, a chimera is an organism containing cells with distinct genetic lineages derived from more than one zygote. This can occur naturally when two fertilized eggs fuse early in development or be produced deliberately through laboratory techniques that introduce donor cells or tissue. A related concept is mosaicism, which arises from post-zygotic mutations within a single zygote.

Natural chimeras have been reported in various species, including humans. In humans, examples include individuals with tissues of different genetic origins or donor-derived cells after bone marrow transplantation. Microchimerism refers to small numbers of cells or DNA from another individual persisting long after exposure.

Chimerism is an area of inquiry in developmental biology and medicine. Researchers study chimeric embryos to understand organ formation and disease, and scientists explore interspecies chimeras to investigate potential avenues for growing human-compatible organs. Clinically, chimerism testing is used to monitor engraftment after transplantation and to assess lineage origin of different tissues. Ethical considerations accompany experiments that create organisms with multiple genomes.

In popular culture, chimeras are often depicted as mythic composites or as scientific possibilities, illustrating the word’s dual heritage in myth and science.