BIO172W08Lec26CT - Biology 172 L e c t u r e 2 6 - P a t t...

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1 March 17, 2008 Today s Outline 1. Finish Friday’s lecture 2. Morphogenesis in Drosophila Maternal effect genes Morphogenetic gradients Segmentation genes Homeotic genes 3. Morphogenesis in Arabidopsis Flower formation Meristems Announcements Exam 3 next Monday March 24 6-8 PM Lectures 18-27 Biology 172 Modification of Cell Cycle (Mitosis) in Early Cleavage Stages Early blastomeres Somatic cells Synthesis M S 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 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 Multicellularity: Pattern Formation and Morphogenesis • Cells in a multicellular organism are specialized (different structures/functions) • Step-wise process of acquiring specialized cellular properties = differentiation 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 How do cells acquire information to specify their position and identity in the embryo? Christiane Nüsslein-Volhard
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This note was uploaded on 12/06/2009 for the course BIO 172 taught by Professor Clark during the Winter '08 term at University of Michigan.

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BIO172W08Lec26CT - Biology 172 L e c t u r e 2 6 - P a t t...

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