Chapter 21 - Chapter 21 The Genetic Basis of Development...

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Chapter 21:   The Genetic Basis of Development From fertilized egg (zygote) to multicellular organism:     Embryonic development involves three major processes: Cell division (mitosis): During early embryonic development, the fertilized egg (zygote) undergoes a series of rapid mitotic  divisions, called “cleavage,” to produce a multitude of cells (see Chapter 47 for diagrams) Differentiation: The process whereby each cell becomes specialized in structure and function (e.g., skin  cells, nerve cells, muscle cells, etc.) Morphogenesis: The physical process of cell arrangement and organization that gives an organism its shape. Early  morphogenetic events result in the establishment of the major body axes (i.e., head—tail,  back—belly). Morphogens are chemicals responsible for body axis development. Later morphogenetic events establish relative locations of structures within smaller  regions of the embryo, such as the appendages (arms, legs, fins, wings, antennae, etc.).  Later events establish the location of specific structures within even smaller region of the  embryo.    But cells are only one level in the hierarchy of structural organization within a multi-cellular organism.  Cells of similar types cooperate  to form tissues; tissues cooperate to form organs; organs cooperate to form systems; systems cooperate to form an organism. Recall the Hierarchy of Structural Organization  from Chapter 1:   organism         organs  tissues      cells Differentiation: During embryonic development, cells change from being unspecialized to becoming specialized in both structure and  function De-differentiation: The ability of a specialized cell to become unspecialized and then give rise to a variety of cells that then differentiate Determination: The molecular events that lead to the point in time when a cell becomes irreversibly  committed to becoming a particular specialized (differentiated) cell Totipotency: The ability of a differentiated cell to de-differentiate, divide and give rise  to all the different types of cells that make up the whole organism Pluripotency: The ability of an undifferentiated cell to differentiate into a variety of (but not all) cell types Apoptosis: A special process of programmed cell death 1 of 19
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Morphogenesis:    The basic body plan is laid out early in development.  Cell division, differentiation and apoptosis play important  roles in shaping the individual.
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Chapter 21 - Chapter 21 The Genetic Basis of Development...

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