topic 9 principles of development f21

topic 9 principles of development f21 - Emily Lin 4/6/2011...

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Emily Lin 4/6/2011 Topic 9: Freeman 21 Ch 21 discusses the principles of development. At the cell level, four processes occur throughout development. Cells divide and begin to express certain genes- a process called differentiation. For the development of individuals from undifferentiated mass of cells, the location, timing and extent of cell division have to be tightly controlled. Apoptosis allows for certain tissues and organs to take shape. Thus, cell division depends on both cell proliferation and loss of cells. During gastrulation, cells rearrange themselves by breaking away and moving to new locations. If this doesn‘t occur properly, embryo may be deformed or die before development is complete. Plant cells do not move but control how the cleavage plane is oriented during cell division and the direction of cell growth that subsequently takes place. Differentiation is the process of becoming a specialized type of cell. It is a progressive step by step process and also, some cells do not become specialized, which are called stem cells. These help replace skin and blood cells that die. The plant equivalent is called a meristem. During development, the most important cell-cell interactions involve sending and receiving signals. Clones are genetically
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topic 9 principles of development f21 - Emily Lin 4/6/2011...

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