In plants, this sort of experiment was considerably aided by another conceptual advance that was as much social as scientific, the development of plant model systems whose intrinsic properties allowed for genetic experimentation, and for facile gene cloning. The ABC model depended on two such systems – Arabidopsis thaliana, whose small genome size allowed map-based cloning (Fig. 1B–D), and Antirrhinum majus, with a highly developed system of transposable element mutagenesis and cloning [39].