Abstract

We have modified an FLP/FRT-based genetic mosaic system to label either neurons derived from a common progenitor or isolated single neurons, in the Drosophila CNS. These uniquely labeled neurons can also be made homozygous for a mutation of interest within an otherwise phenotypically wild-type brain. Using this new mosaic system, not only can normal brain development be described with unprecedented single cell resolution, but also the underlying molecular mechanisms can be investigated by identifying genes that are required for these developmental processes. Since Ramon y Cajal and his contemporaries first investigated the diverse and intricate neuronal morphologies in the brain 1 , significant progress has been made in describing the formation of neural circuits based on the projection patterns of single neurons (reviewed in