MCD BIO 138 Lecture Notes - Lecture 6: Syncytium, Pattern Formation, Blastoderm
4 Jun 2019
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Lec 6 maternal control of pattern formation in early fly embryos: patterning happens in syncytial blastoderm stage. Have tf e. g. bicoid acting as localized determinants, but tfs never secreted from the cell. So only way to have tf acting directly as morphogen & get into direct concentration gradient is to have syncytial arrangement of nuclei. Once embryo gets cellularized, if want cells to know their positions along axis relative to other cells, then need secreted signaling molecules that can form gradient & be received on cell surface. Point: needs to be present in oocyte before fertilization: transcribed in mother during oogenesis (have to have proteins), not required at other times, some maternal effect genes encode proteins and mrna needed to support early cleavage stages. Localized e. g. : germ cell determinants, bicoid and nanos. Morphogen: key attributes: concentration gradient (doesn"t matter what shape it is)
