In discussions of the relevant importance of genetic and environmental influences on the development of the individual, it's often stated that the genetic and environmental influences interact. An example that is often given is a certain kind of rabbit (usually white), carrying a particular gene for fur color. When the proper allele is present, AND the rabbit is exposed to cold, it will a dark spot on its fur. When the allele is present, the dark spot does not develop without the cold, and when the rabbit has the opposite allele, the spot will not develop even with cold exposure.
This is fine, but when I want to explain genes and environment to people, it has two pedagogical flaws: (1) it's about rabbits (2) it's about a trait people don't really care about
Is there a human example of this phenomenon? That is, a phenotype which requires BOTH a certain genetic background and particular environmental influences in order to be expressed?