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Abstract:
The longitudinal pattern of the Drosophila embryo is controlled by the concerted activity of gene products provided during oogenesis (maternally active genes) and embryogenesis (zygotically active genes). An initially relatively coarse system of positional information laid down by maternal gene products becomes successively refined towards the repeating pattern of segments first by the division into domains by the products of the zygotic gap genes and subsequently by the action of pair-rule and segment-polarity genes (Nüsslein-Volhard & Wieschaus, 1980; Ingham & Martinez-Arias, 1986; Ingham, 1988; for review see Akam, 1987). Maternal genes affecting anteroposterior pattern have been classified into three groups according to their phenotype: the terminal group, the anterior group and the posterior group (Nüsslein-Volhard et al. 1987). Together the three maternal gene groups control the establishment of the entire segmental pattern. Embryos that lack all maternal information show no anteroposterior pattern (Nüsslein-Volhard et al. 1987, R.L. unpublished data).
