06-Developmentnotes

06-Developmentnotes - Cellular mechanisms of development...

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Unformatted text preview: Cellular mechanisms of development Overview of development Development is the successive process of planned, gene-directed changes throughout an organisms life cycle. There are four processes that bring about the changes of development. The four subprocesses: 1. Cell division and cleavage 2. Differentiation 3. Pattern formation 4. Morphogenesis Morphogens Morphogens are molecules that affect developmental fate They initiate and terminate the four processes They also bring about cell determination Morphogens can be proteins, mRNAs or other molecules They can be obtained in a couple different ways: o Inherited in cytoplasm from the egg: Cytoplasmic determinants o Received as signals from other cells: Induction agents Cytoplasmic determinants Deposited in egg cytoplasm during oogenesis o Cytoplasm contains many different determinants o Each is localized to particular part of the egg o Cells inherit a portion of the egg cytoplasm; thus different sets of cytoplasmic determinants o Puts cells on different developmental trajectories o Especially active early in development Induction Induction influences the fate of a cell due to interaction with nearby cells Certain embryonic cells produce signaling proteins o These are secreted into ECM o Spread to nearby cells o Cells are stage specific Concentration is the lightest near cells that secrete signaling proteins o Induce a concentration-dependent response o Also creates a series of cell types/ gradient of changes Cell division and cleavage The diploid zygote undergoes a period of rapid mitotic divisions o In animals, this period is called cleavage o The G1 and G2 phases are shortened or eliminated o Overall zygote size remains unchanged and no growth o The number of cells increases o The result: an embryo consisting of a larger and larger number of smaller and smaller cells o Each of the resulting cells is identical and is called a blastomere Blastocyst The cleavage in mammals continues for 5-6days o Each blastomere has a very small localized amount of egg cytoplasm o It also inherits specific subsets of morphogens o Blastocyst produces a ball of blastomeres o The ball of blastomeres is hollow and the central cavity is called the blastocoel The blastocyst consist of: o The outer layer is called the placenta o The inner cell mass is called the embryo o It is the source of embryonic stem (ES) cells Blastomeres Blastomeres: have an undetermined fate and therefore give rise to any cell type Stem cells:...
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This note was uploaded on 04/11/2011 for the course BIO 111 taught by Professor Dr. bos during the Winter '10 term at Purdue.

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06-Developmentnotes - Cellular mechanisms of development...

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