rav65819_ch19_369-394

rav65819_ch19_369-394 - ; 19 4000 m chapter Cellular...

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;;;;;;;;;;;; 19 4000 m μ chapter Cellular Mechanisms of Development
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introduction 19.1 Overview of Development 19.2 Cell Division Development begins with cell division Every cell division is known in the development of C. elegans Stem cells continue to divide and can form multiple kinds of tissue Plant growth occurs in speciFc areas called meristems 19.3 Cell Differentiation Cells become determined prior to differentiation Determination can be due to cytoplasmic determinants Induction can lead to cell differentiation Reversal of determination has allowed cloning Reproductive cloning has inherent problems Therapeutic cloning is a promising possibility Stem cell research has stimulated ethical debate Adult stem cells may offer an alternative to ES cells 19.4 Pattern Formation Drosophila embryogenesis produces a segmented larva Morphogen gradients form the basic body axes in Drosophila The body plan is produced by sequential activation of genes Segment identity arises from the action of homeotic genes Pattern formation in plants is also under genetic control 19.5 Morphogenesis Cell division during development may result in unequal cytokinesis Cells change shape and size as morphogenesis proceeds Programmed cell death is a necessary part of development Cell migration gets the right cells to the right places In seed plants, the plane of cell division determines morphogenesis 19.6 Environmental Effects on Development The environment affects normal development Endocrine disrupters can perturb development COUNTLESS GENERATIONS OF YOUNG children have reveled in the discovery of frog tadpoles during summer visits to freshwater ponds, have watched with fascination as a chick pecks its way out of its shell, or have delighted as the first flowers of spring push their way up through the soil. For thousands of years, the wonder of such events has inspired a desire to understand how organisms arise, grow, change, and mature. We have explored gene expression from the perspective of individual cells, examining the diverse mechanisms cells employ to control the transcription of particular genes. Now we broaden our perspective and look at the unique challenge posed by the development of a single cell, the fertilized egg, into a multicellular organism such as is occurring in these fish embryos.
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In the course of this developmental journey, a pattern of decisions about gene expression takes place that causes particular lines of cells to proceed along different paths, spinning an incredibly complex web of cause and effect. Yet, for all its complexity, this developmental program works with impressive precision. In this chapter, we explore the mechanisms of development in
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rav65819_ch19_369-394 - ; 19 4000 m chapter Cellular...

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