Devel.Concepts.Genes.08

Devel.Concepts.Genes.08 - 0 NOTE! These files are provided...

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0 NOTE!! These files are provided for the sole purpose of assisting BSci 110 students to study for exams in the class. Some of the material in these files may be copyrighted, and it is not OK for you to share these files with anyone who is not a student in this class or to use them for any purpose other than to study for the exams of our class. Thanks, Carl Johnson
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1 How do we come to be as we are? How can a complex organism come from an apparently simple cell like a zygote? epigenesis? Derived from Aristotle: the form of an animal was thought to emerge gradually from the relatively formless zygote. preformation? For example, the "homunculus:" Conceptual/Genetic Bases of Development
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2 Some definitions : "Housekeeping" proteins vs. cell-type specific proteins. Determination : not visible, but irreversible commitment to differentiation. Differentiation : expression of the developmental commitment. Usually involves synthesis of cell-type specific proteins. Morphogenesis : shaping of the multicellular body and its organs; pattern formation. analogies to photography : exposure of the film. chemical development of the negatives. Conceptual/Genetic Bases of Development
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3 Determination can be assessed by transplantation experiments. This slide shows a case where the donor tissue was not yet determined Purves 19.2 Conceptual/Genetic Bases of Development Fate: skin Fate: brain Fate: notochord (would have become skin) When transplanted to "brain" position, the donor tissue becomes brain tissue When transplanted to "notochord" position, the donor tissue becomes notochord tissue
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4 Not determined: Determined: Conceptual/Genetic Bases of Development extra neural plate is formed
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Conceptual/Genetic Bases of Development A molecular example of the Determination-to-Differentiation Transition: muscle cell differentiation 1.Determination: signals from other cells lead to activation of myoD (a T.F. gene); this irreversibly commits the cell to becoming a skeletal muscle cell. 2. Differentiation: synthesis of MyoD protein further stimulates myoD and ultimately other muscle cell-specific genes such as myosin. MyoD also turns on genes that block cell division, leading to multinucleate muscle cells. 5 Undetermined
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Conceptual/Genetic Bases of Development 6 Two important developmental issues related to genetics: How does the zygote know which species to develop from its genetic information? How are the genes regulated to make brain cells in one place and intestinal cells in another? (i.e., to turn on genes that make cell- type specific proteins in the correct places)
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7 What are the determinants that convert a "formless" egg into a complex organism? Are there different factors that are segregated differentially to different cells in the embryo? Weismann's Hypothesis (1892)
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This note was uploaded on 04/07/2008 for the course BSCI 110B taught by Professor Due during the Spring '08 term at Vanderbilt.

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Devel.Concepts.Genes.08 - 0 NOTE! These files are provided...

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