Practice question

Drosophila exhibits superficial cleavage where nuclear division occurs without cytoplasmic division. Zygote nucleus undergoes rapid synchronous mitoses within central cytoplasm, producing multinucleate syncytium. Around nuclear cycle 10, nuclei migrate peripherally into cortical cytoplasm, arranging beneath plasma membrane. Actin caps form above each nucleus, but no cell membranes separate nuclei, defining syncytial blastoderm. Only at cycle 14 does membrane invagination occur simultaneously around every cortical nucleus, converting syncytium into cellular blastoderm of epithelial monolayer surrounding central yolk. This syncytial stage allows rapid diffusion of morphogens like Bicoid essential for patterning.