The fruitless (fru) gene, linked to courtship behavior in fruit flies and conserved across many insect species, operates differently in two fruit fly species, Drosophila melanogaster and Drosophila virilis. Despite the gene's association with male courtship behaviors, experiments using CRISPR-Cas9 technology to add fru to females of D. virilis demonstrated unique outcomes compared to D. melanogaster, suggesting that conserved genes do not guarantee identical functions across species.
