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Chapter 21 The Genetic Basis of Development Chapter 21 The Genetic Basis of Development Embryonic development involves: •Cell division •Cell differentiation •Morphogenesis Chapter 21 The Genetic Basis of Development Model organisms: Chapter 21 The Genetic Basis of Development Model organisms: fruit fly Chapter 21 The Genetic Basis of Development Model organisms: nematode Chapter 21 The Genetic Basis of Development Model organisms: zebra fish Chapter 21 The Genetic Basis of Development Model organisms: common wall cress Chapter 21 The Genetic Basis of Development Different kinds of cells have the same DNA Chapter 21 The Genetic Basis of Development Different kinds of cells have the same DNA. Totipotent: able to divide to produce an entire new organism (most plant cells, some animal cells). Chapter 21 The Genetic Basis of Development Different kinds of cells have the same DNA. Pluripotent: able to reproduce and differentiate in vitro and in vivo (stem cells). Chapter 21 The Genetic Basis of Development Different kinds of cells make different proteins thru regulation of gene transcription Chapter 21 The Genetic Basis of Development Different kinds of cells make different proteins thru regulation of gene transcription. Regulation is directed by maternal molecules in the cytoplasm and by signals from neighboring cells. Chapter 21 The Genetic Basis of Development Pattern formation: development of spatial organization Chapter 21 The Genetic Basis of Development Pattern formation: development of spatial organization. Continuous in plants, but for animals it takes place only in embryos and juveniles Chapter 21 The Genetic Basis of Development Pattern formation: development of spatial organization. Continuous in plants, but for animals it takes place only in embryos and juveniles. Positional information along axes and in relation to neighbors. Chapter 21 The Genetic Basis of Development Life Cycle of Drosophila Chapter 21 The Genetic Basis of Development Life Cycle of Drosophila 1. For the first ten cell divisions, there is no cell growth and no cytokinesis. You end up with one big multinucleated cell. Chapter 21 The Genetic Basis of Development Life Cycle of Drosophila 2. At the tenth division, nuclei migrate to the periphery of the embryo. Chapter 21 The Genetic Basis of Development Life Cycle of Drosophila 3. At division 13, plasma membranes finally begin to partition the 6000 or so nuclei into separate cells. The body plan and segments are already determined. Chapter 21 The Genetic Basis of Development Life Cycle of Drosophila 4. Visible segments form. They look very much alike. Chapter 21 The Genetic Basis of Development Life Cycle of Drosophila 5. Some cells move to new positions. Organs form. The wormlike larva hatches. The larva eats, grows, and molts through three larval stages. Chapter 21 The Genetic Basis of Development Life Cycle of Drosophila 6. The larva forms a pupa in an enclosed case. Chapter 21 The Genetic Basis of Development Life Cycle of Drosophila 7. Metamorphosis occurs inside the pupa. When the adult hatches, each segment is anatomically distinct. Chapter 21 The Genetic Basis of Development Egg polarity genes Chapter 21 The Genetic Basis of Development Egg polarity genes are “maternal effect genes” Chapter 21 The Genetic Basis of Development Egg polarity genes are “maternal effect genes.” They produce proteins called morphogens Chapter 21 The Genetic Basis of Development Egg polarity genes are “maternal effect genes.” They produce proteins called morphogens. A morphogen gradient establishes the anteriorposterior axis. Chapter 21 The Genetic Basis of Development Bicoid is a gene in the mother that produces a two-tailed offspring. Chapter 21 The Genetic Basis of Development Segmentation genes act in a cascade, directing the formation of segments Chapter 21 The Genetic Basis of Development Segmentation genes act in a cascade, directing the formation of segments. Their products are transcription factors for other genes. Chapter 21 The Genetic Basis of Development Segmentation genes act in a cascade, directing the formation of segments. Their products are transcription factors for other genes. Chapter 21 The Genetic Basis of Development Homeotic genes control the growth of specific organs. Chapter 21 The Genetic Basis of Development gene function maternal effect egg polarity segmentation: •gap •pair-rule •segment polarity coarse subdivision further subdivision orientation of seg’s homeotic specific organs Chapter 21 The Genetic Basis of Development gene function maternal effect egg polarity Chapter 21 The Genetic Basis of Development gene function maternal effect egg polarity mutation Chapter 21 The Genetic Basis of Development gene function gap coarse subdivision Chapter 21 The Genetic Basis of Development gene function gap coarse subdivision mutation Chapter 21 The Genetic Basis of Development gene function pair-rule further subdivision Chapter 21 The Genetic Basis of Development gene function pair-rule further subdivision mutation Chapter 21 The Genetic Basis of Development gene function segment polarity further subdivision Chapter 21 The Genetic Basis of Development gene function segment polarity further subdivision mutation Chapter 21 The Genetic Basis of Development gene function homeotic specific organs Chapter 21 The Genetic Basis of Development gene function homeotic specific organs mutation Chapter 21 The Genetic Basis of Development Homeobox (hox) genes have been highly conserved Chapter 21 The Genetic Basis of Development Homeobox (hox) genes have been highly conserved. Chapter 21 The Genetic Basis of Development Neighboring cells instruct other cells to form particular structures Chapter 21 The Genetic Basis of Development Neighboring cells instruct other cells to form particular structures. nematode gonad vulva Chapter 21 The Genetic Basis of Development gonad vulva Chapter 21 The Genetic Basis of Development epidermis outer vulva inner vulva gonad vulva Chapter 21 The Genetic Basis of Development anchor cell precursor cells Chapter 21 The Genetic Basis of Development The anchor cell secretes a first inducer Chapter 21 The Genetic Basis of Development The anchor cell secretes a first inducer. The inducer binds to receptors on the nearest cell (where the concentration is highest) Chapter 21 The Genetic Basis of Development The anchor cell secretes a first inducer. The inducer binds to receptors on the nearest cell (where the concentration is highest). That cell begins to develop into the inner vulva Chapter 21 The Genetic Basis of Development The inner vulva cell secretes a second inducer Chapter 21 The Genetic Basis of Development The inner vulva cell secretes a second inducer. The second inducer binds to receptors on neighboring cells Chapter 21 The Genetic Basis of Development The inner vulva cell secretes a second inducer. The second inducer binds to receptors on neighboring cells. They begin to develop into outer vulva. Chapter 21 The Genetic Basis of Development If you surgically remove the anchor cell from the embryo, the nematode develops without a vulva.