Genes Affecting the Segmental Subdivision of the Drosophila Embryo

Segmentation is the process that subdivides an initially uniform blastoderm into a series of repeating homologous units, the segments. In Drosophila, a number of genes have been identified that are involved in segmentation (Nüsslein-Volhard and Wieschaus 1980; Nüsslein-Volhard et al. 1982, 1984; Jürgens et al. 1984; Wieschaus et al. 1984a). For a complete and comprehensive understanding of the process, genetic analysis must proceed basically in two directions: (1) identification of all the relevant genes by mutations that lead to an altered segmentation pattern and (2) evaluation of the role of each individual gene in the process by studying its phenotype, its developmental effects, and finally its molecular biology. While the screens for maternal mutants have not yet reached saturation, most, if not all, of the genes required specifically in the zygote are known. The initial phenotypic analysis grouped these zygotic genes, according to the level of spatial organization affected in...