PATTERN-FORMATION BY TRANSCRIPTIONAL CASCADES IN THE DROSOPHILA EMBRYO

Genetic and molecular analyses have combined to yield insights into fu nctional cascades of transcription factors necessary to establish the molecular blueprint of the Drosophila body pattern in response to posi tional information already present in the egg. This maternal informati on is based on a small set of asymmetrically distributed maternal tran scription factors that act as graded morphogens along the anterior-pos terior and the dorsal-ventral axes of the embryo. Recent progress in t he field provides first insight into the molecular mechanisms by which long-range positional information in the egg causes a series of local ized zygotic transcription factor gradients to position development fa te along the axes of the blastoderm embryo.