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Embryonic Development of Multicellular Organisms
Chapter 21
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Embryonic Development: Zygote Organism
Cell Division: large # identical cells through mitosis Cell Differentiation: cells become specialized in structure & function Morphogenesis: “creation of form” – organism’s shape
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Determination: irreversible series of events that lead to cell differentiation
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Cytoplasmic determinants: maternal substances in egg distributed unevenly in early cells of embryo
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Induction: cells triggered to differentiate
Cell-Cell Signals: molecules produced by one cell influences neighboring cells Eg. Growth factors
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Pattern formation: setting up the body plan (head, tail, L/R, back, front)
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Morphogens: substances that establish an embryo’s axes
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Homeotic genes: master control genes that control pattern formation (eg. Hox genes)
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Evolving Switches, Evolving Bodies
HHMI Short Film
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Pitx1 Gene = Homeotic/Hox Gene
Stickleback Fish Humans Development of pelvic bone Development of anterior structures, brain, structure of hindlimb Mutation may cause clubfoot, polydactyly (extra fingers/toes), upper limb deformities
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Summary Embryonic development occurs when gene regulation proceeds correctly Cancer occurs when gene regulation goes awry
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