MOLBIOL 3M03 Lecture 4: Lecture 4 - Drosophila
19 Mar 2017
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Document Summary
Insects undergo superficial cleavage large mass of centrally located yolk confines cleavage to the cytoplasmic rim of the egg. In this cleavage pattern cells do no form until after the nuclei have divided several times. In drosophila egg karyokinesis (nuclear division) occurs without cytokinesis (cell division) to create syncytium. Syncytium single cell with many nuclei residing in a common cytoplasm. Zygote nucleus undergoes several mitotic divisions within the central position of the egg. At cycle 10 the other nuclei migrate to the cortex (periphery) and mitosis continues at a slower rate. During nuclear division the embryo is syncytial blastoderm no cell membranes exist other than that of the egg. When the nuclei reach the periphery of the egg during the 10th cleavage cycle each nucleus becomes surrounded by microtubules and microfilaments. 1st phase of blastoderm cellularization is characterized by invagination of cell membranes between nuclei to form furrow canals.
