Fig. 1. (A) Schematic of mushroom body development [adapted, with permission, from Lee et al. (Lee et al., 1999)]. The three colors represent three classes of MB neurons born at different developmental windows as indicated. (B) Schematic of the genetic scheme for MARCM-based mosaic screen on chromosome arm 2R. (C) Three types of labeled MARCM clones of MB neurons can be generated by heat-shock induction of FLP recombinase. If mitotic recombination occurs in a dividing neuroblast (Nb), and if the regenerating neuroblast loses the repressor for marker expression, a labeled neuroblast clone is generated (boxed). If the ganglion mother cell (G) loses the repressor, a two-cell clone is generated (not shown). If mitotic recombination occurs in a dividing ganglion mother cell, one postmitotic neuronal progeny (N) loses the repressor resulting in a single-cell clone (arrowhead).