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Unformatted text preview: Chapter 19 Cellular Mechanisms of Development 02/03/2008 20:18:00 Development process Growth (cell division) Differentiation o Changes in gene expression result in differences between cells that ultimately result in cell specialization o Certain genes expressed at certain times but others may not be expressed at all Pattern formation o Cells become oriented into body plan o Cells ability to detect positional information that guides their ultimate fate. Morphogenesis o Form of body is generated: organs, anatomical features o Involves cell death and division/differentiation Immediately after fertilization, zygotes perform mitotic division rapidly Cell division following fertilization is called cleavage, forms many smaller cells into blastomeres o Not accompanied by any increase in overall size of embryo, G1 and G2 phases are extremely shortened In the course of development, cells become different from one another because of the differential expression of subsets of genes not only at different times, but at different locations of the growing embryo. Differentiated cells are distinguished based on what proteins they synthesize, their morphologies, and their specific function Cells initiate developmental changes by using transcription factors to change patterns of gene expression. Stem cells are derived from blastocyst stage embryos Pattern formation follows from positional information A cell changes gene expression based on what part of the body it is in Can be considered the process of taking a radially symmetrical cell and imposing two perpendicular axes to define the basic body plan, which becomes bilaterally symmetrical 02/03/2008 20:18:00 02/03/2008 20:18:00 ...
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- Spring '06