development_wn2

development_wn2 - Brain Structure Read pp. 64-80 in...

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Webnotes Seven stages of development Genetic influences in simple organisms Combining genetic and environmental cues on flies Read pp. 64-80 in addition to required reading on web Brain Structure Formation of the early nervous system in verts. Axon outgrowth and pathfinding Synapse Formation Developmental plasticity
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Webnotes How does a complex adult nervous system develop from the egg, a single cell? Development of the nervous system Stages of Nervous System Development (not necessarily in this order) 1) Cell proliferation The single egg cell needs to undergo many cycles of cell division in order to give rise to the adult nervous system. The human brain alone contains ~10 12 neurons, and this is not even considering other cell types in the brain, plus the spinal cord and the peripheral nervous system. 2) Migration. Cells are often not born at the location they need to be in the adult nervous system. Therefore they have to move around during development. 3) Cell death. Depending on the species of animal, between 10% and 50% of cells which are born during the development of the nervous system will die before the animal is mature. This process plays an important role in development, and mutations which prevent cell death are lethal to the animal. 4) Differentiation. Precursor cells early in development are undifferentiated. These precursors produce final differentiated cell types which have specific anatomical, physiological and biochemical features. 5) Axon growth and pathfinding. Neurons need to make proper connections with other neurons or target tissues. Some neurons, like the sensory neuron in Duck Man, must send out axons for very long distances to find their targets. 6). Synapse formation After the axons reach their target, they must form synapses to allow communication with the target cell. 7). Developmental plasticity After synapses form, connections can be selectively strengthened or eliminated to ensure that the proper information will be carried by the pathway. simple organisms tend to rely more on genetics 1) 2) complex organisms tend to rely more environmental cues simple organism , the worm C. elegans Single gene mutations in C. elegans can radically alter cell fate, cell migration, and cell death in this animal. Environment during development almost never affects C. elegans the cell’s fate Genetic influences in simple organims
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Webnotes - We will discuss 2 mutants Ommatidia development in flies environment + genetics . - Flies have compound eyes with many separate small retinas - Each ‘retina’ called ommatidia . - Each ommatidum has 8 different photoreceptors - Each photoreceptor has a different wavelength sensitivity (like our 3 types of cones). - Only one photoreceptor, #7 , is sensitive to ultraviolet light . -Mutants lacking photoreceptor #7 can’t see ultraviolet light , and therefore are easily identified.
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Webnotes - BOS shows interaction of genes and environment influence the development of photoreceptor 7.
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This note was uploaded on 12/10/2008 for the course NPB 100 taught by Professor Chapman during the Fall '08 term at UC Davis.

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development_wn2 - Brain Structure Read pp. 64-80 in...

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