Molecular characterization of genes led to the insight, that flies and mammals are much more similar as initially anticipated. Principle mechanisms underlying cell signaling are used for the communication of cells in different contexts. The molecular control of eye development may serve as a prominent example. Also within the one organism, the same gene is often reused. Notch for example functions in at least six different processes in Drosophila development and is conserved between worms, flies, frogs and mice. The study of these signaling cascades therefore has a broad implication.

But the conservation between insects and mammals goes beyond that. Gene complexes and developmental processes are also homologous. The most famous example to illustrate this fact is the conservation of homeotic gene clusters. In insects and mammals, homeotic genes are arranged in a similar way on the chromosome and their linear array reflects their function in segment identity from posterior to anterior.