BIOL 3530 Lecture 2: Chapter 2
7 Oct 2016
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Chapter 2: development of the drosophila body plan. The drosophila egg is the shape of a sausage. It has a micropyle at the anterior end (site of sperm entry). With fertilization, the fusion of nuclei is followed by rapid mitotic divisions (90 minutes) and no cleavage. After nine divisions, nuclei move to the periphery to form the syncytial blastoderm (2 hours). By 13 mitoses the membranes sprout to surround the nuclei to form cells (cellular blastoderm). ~15 cells at posterior (pole cells) are sequestered and become the germline. During first ~3 hrs. large molecules such as proteins can move between nuclei until the cellularization occurs. Single layer of cells give rise to all tissues. Gastrulation starts at ~3 hrs: mesoderm forms from ventral tissue, midgut from endoderm at the anterior and posterior ends, ectoderm remains on outside. The mesodermal tube forms from ventral tissue then cells separate & move to internal locations under the ectoderm.
