© 1982 by The Society for Integrative and Comparative Biology
Determination in Drosophila Embryos1
Department of Zoology, University of Washington Seattle, Washington 98195
Biology Division, Oak Ridge National Laboratory Laboratory, Oak Ridge, Tennessee 37830
SYNOPSIS. In this review we describe data of experiments which interfere with the formation of the metameric pattern during embryogenesis. Ligating embryos before blastoderm stage leads to a gap in the segmentation pattern of the differentiated embryo. The gap can extend up to 6 segments but terminal segments are always recognizable. In posterior but not in anterior fragments we find abnormally large but fewer segments. This increase in segment size results from a different determination of blastoderm cells after ligation. During nuclear multiplication stages when a gap can be produced, the zygotic genome is not yet active. Information to develop the metameric pattern in ligated embryos must therefore have been made during oogenesis.
Recently Nüisslein-Volhard and Wieschaus (1980) have described three zygotic mutations which form embryos with a gap of segments similar to our ligated embryos. We have discussed these mutant phenotypes in connection with our experimental data.
Segmentation is controlled at several levels. During oogenesis the anterior-posterior and dorsal-ventral axes become established (Nüsslein-Volhard, 1979). Also during oogenesis, but extending into early embryonic life, information is generated to subdivide the embryo into blocks of cells forming the metameric pattern. At blastoderm the identity of segments becomes established.