Practice question

Antennapedia is archetypal homeotic mutant discovered by Balkaschina. Dominant chromosome inversion places Antennapedia gene under eye-antennal enhancers causing ectopic expression in antennal disc. Antennapedia protein promotes thoracic leg programs including expression of homothorax and represses antennal determinants like Distal-less. Resultant antenna-to-leg transformation yields mesothoracic legs complete with claws emerging from head socket where antennae normally reside. Phenotype demonstrates selector gene instructive sufficiency: ectopic expression alone redirects imaginal disc fate from antenna to leg, establishing principle of master regulatory genes and providing molecular basis for homeosis concept central to evolutionary developmental biology and appendage diversification mechanisms.