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Unformatted text preview: Epigenesis vs preformation- epigenesis – complexity of an organism that arises through the interaction of simpler parts- preformation – hypothesis that all organs were developed in the embryo in miniature forms What is the organizer ? - sends signals to surrounding tissues- “remembers” its own fate when placed in a new environment (dorsal lip of blastopore)- Spemann/Mangold What is fate mapping ? - Vogt, dyed cells in a blastocyst and watched where the cells moved while differentiating- a cell’s ancestry is sometimes crucial for its differentiation and behavior, and we need to know that ancestry in detail to interpret “disruption” experiments Be sure you are familiar enough with the “big ideas” to provide definitions (e.g. differentiation , morphogenesis ). - differentiation – process by which differing properties are conferred on parts of the embryo at different times and in specific locations- specialized structures arise in a reliable fashion in a mature organism- morphogenesis – how form arises; organization of the cells of the body into functional structures- pattern formation – how different parts become highly ordered spatially What is conditional specification ? - Hans Driesch and sea urchins- differentiation of a cell or tissue depends on its local environment; easy to change- ability of cells to achieve their respective fates by interacting with other cells; relies on paracrine factors secreted by neighboring cells Autonomous specification ? - ascidians- differentiation occurs how it would normally when separated or intact; does not change when isolated or forced to change- differentiation in which the blastomere inherits a determinant, usually a set of transcription factors from the egg cytoplasm; these factors regulate gene expression to direct cell Totipotency ? capable of producing all the different tissues of the body (cells of an 8-cell embryo) Pluripotency? capable to make many cell types Multipotency? able to make several different cell types (adult stem cells) What is " mosaic development "? - when most cells of an early embryo are determined by autonomous specification- develop like a mosaic of individually laid tiles – with each cell receiving its instructions independently, without cell-cell interactions Localized determinants ? - autonomous specification; can be sufficient, necessary, or both; transcription factors which influence cell development How does one show sufficiency of a group of cells (or a molecule) for some developmental process?- sufficiency – when a group of cells is added to a cell, embryo, or tissue, it confers the ability to differentiate in a particular way- does not mean a group of cells is necessary for differentiation How does one show necessity ?...
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This note was uploaded on 02/29/2012 for the course ZOOLOGY 470 taught by Professor Hardin during the Spring '12 term at University of Wisconsin.
- Spring '12