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Unformatted text preview: DEVELOP MENTAL GENET ICS OF DROSOPH I LA , PART I Klug pg. 575 586; 541 543; & Fig. 8-22 23.1 Developmental Genetics Seeks to Explain How a Differentiated State Develops from an Organisms Genome- development : attainment of a differentiated state by all the cells in an organism-cells get to the undifferentiated to the differentiated state through a process that involves the progressive activation of different gene sets in different cells of the embryo-the idea that differentiation is accomplished by activating and inactivating genes at different times and in different cell types is called the variable gene activity hypothesis 23.2 Conservation of Developmental Mechanisms and the Use of Model Organisms-many developmental mechanisms are similar among all multicellular animals-in higher eukaryotes, development begins with the formation of the zygote, a cell generated by the fusion of the sperm and the oocyte. Following fertilization, the nuclei of progeny cells are in different environments as the maternal cytoplasm is dist. into the new cells. In different cells, the cytoplasm exerts diff. influences on the genetic material, causing differential transcription at specific points during development. As embryonic cells respond to their continually changing external and internal environments, they embark on a developmental pathway. Selection of a specific developmental pathway for a cell involves action by a single master gene that initiates a cascade of expression by other genes....
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- Spring '08