Final answer:
The provided information does not mention a specific gene responsible for heart development shared by fruit flies and humans. The excerpts discuss genetics and the application of fruit fly research to human genetic understanding.
Step-by-step explanation:
The question relates to the gene in fruit flies and humans that is responsible for the normal development of the heart. However, there appears to be a discrepancy as the question mentions a vignette "A Fly Without a Heart," yet the provided excerpts do not discuss a particular gene responsible for this trait. Instead, they focus on different aspects of genetics, including X-linked traits, the inheritance of these traits, and the importance of Hox genes in body plan development.
Moreover, the provided excerpts mention that discoveries in fruit fly genetics can be applied to human genetics, highlighting the principle that core genetic mechanisms are often conserved across species. This conservation is why fruit fly (Drosophila) research is valuable; their genetic pathways can illuminate similar processes in humans.