From gradients to stripes in Drosophila embryogenesis: filling in the gaps.

Pattern formation along the anterior-posterior axis of the Drosophila embryo is organized by asymmetrically distributed maternal transcription factors. They initiate a cascade of spatially restricted and interacting zygotic gene activities that provide a molecular blueprint of the larval body at blastoderm stage. The key players in the pattern forming process have been identified. Recent progress has begun to reveal the mechanisms by which coherent positional information of maternal origin becomes transferred into serially repeated zygotic gene expression domains reflecting the metameric body plan of the larva.