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Chapter 19 Cellular Mechanisms of Development 19.1 Process of Development 4 sub-phases Cell division (mitosis) Differentiation (specialization) Pattern formation (body plan orientation) Morphogenesis (body form generation) 19.2 Cell Division Control over cell cycle checkpoints Rapid division following fertilization (cleavage) 19.3 Cell Differentiation Cell determination commits a cell to a developmental pathway Cytoplasmic determinants (from egg cell) Cell to cell interactions (induction) Stem cells – capable of both continual division and differentiation Totipotent Pluripotent Multipotent Unipotent 19.4 Nuclear Reprogramming The more differentiated cells are the harder it is for them to start over. Somatic cell nuclear transfer (Dolly) Problems with this approach seem to stem from our inability to successfully rewind molecular clocks Therapeutic cloning 19.5 Pattern Formation Positional information can regulate gene expression Early in development basic body plan forms by sequential gene activation Dorsal / ventral Anterior / posterior Homeotic genes are master genes for body segment development 19.6 Morphogenesis Morphogenesis is the product of changes in cell structure and behavior Unequal division of cytoplasm Change in cell shape or size Apoptosis Cell migration