Long ago, a "Chimera" was a terrifying Greek monster—part lion, goat, and snake. Today, the story is more grounded: scientists use the term for any organism containing .
Read Theory tests your attention to detail. A common wrong answer is "an organism with DNA from two different species." While that can be a chimera, the biological definition is broader: two distinct fertilized eggs (zygotes) fusing. The passage emphasizes that even two human twins fusing creates a chimera, no other species needed.
A popular real-world example often linked to these lessons is the story of . She nearly lost custody of her children because DNA tests claimed she wasn't their mother. It turned out she was a human chimera; she had absorbed a twin in the womb, meaning her skin and blood had one set of DNA, while her reproductive system had another.