BIO172W08Lec26CT - Biology 172 Lecture 26 - Pattern...

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March 17, 2008 Today’s Outline 1. Finish Friday’s lecture 2. Pattern Formation & Morphogenesis in Drosophila Maternal effect genes Morphogenetic gradients Segmentation genes Homeotic genes 3. Pattern Formation & Morphogenesis in Arabidopsis Flower formation Meristems Announcements Exam 3 next Monday March 24 6-8 PM Lectures 18-27 Biology 172
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Modification of Cell Cycle (Mitosis) in Early Cleavage Stages Early blastomeres Somatic cells Synthesis M S
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Eggs are Asymmetric Cytoplasmic determinants = molecules in egg cytoplasm that directs early development Maternal effect genes = phenotype of embryo controlled by genotype of mother in situ hybridization
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Activating the Zygotic Genome During early cleavage stages (cell cycle = M+S) no RNA transcription occurs Cytoplasmic determinants (maternal contributions of protein, RNA, etc . stored in the oocyte) control development RNA transcription (from the zygotic genome ) begins when G1 and G2 are added to the cell cycle after several cleavages Mammals are an exception: zygotic transcription is initiated at the two-cell stage
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Multicellularity: Pattern Formation and Morphogenesis Cells in a multicellular organism are specialized (different structures/functions) Step-wise process of acquiring specialized cellular properties = differentiation Differentiated cells are organized into tissues & organs according to a specific plan/blueprint = morphogenesis Patterns of development are established early in embryogenesis = pattern formation Individual cell fate depends on position in the embryo and interaction with other cells
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How do cells acquire information to specify their position and identity in the embryo? Christiane Nüsslein-Volhard
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BIO172W08Lec26CT - Biology 172 Lecture 26 - Pattern...

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