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Cards In This Set
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What is the common pattern to bones of tetrapods? describe each
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Stylopod - proximal - humerus/femur
zeugopod - middle - radius/ulna, fibula, tibia autopod - distal - fingers toes |
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What are the 3 axes of the vertebrate limb?
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Proximal-distal - stylo-zeugo-auto
ant-pos - thumb ant - pinky pos dorsal-ventral - knuckles dorsal, palm - ventral |
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What is pattern formation?
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The process by which embryonic cells form ordered spatial arrangements of differentiated tissues
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Where do limbs form?
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They don't just form anywhere along the body axis, there are discrete positions where they are generated
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What are the experiments that determine which areas limbs form?
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1. deleting groups of cells and observing that no limbs grow in their absence
2. transplanting a group of cells to a different location and observing that they develop a new limb 3. injecting radioactive precursor/ dye into cells and observing that their descendants partake in limb development |
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What is a limb field?
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The entire area that is capable of forming a limb?
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How does limb development begin?
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Mesenchymal cells from the somatic region of the lateral plate mesoderm proliferate. mesenchymal cells from the somites at the same level also proliferate
these mesenchymal cells accumulate and form the limb bud |
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How many limbs are formed for tetrapods? how are they related to one another?
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4
theyre always opposite each other across the midline they develop at different somite locations but are constant with respect to hox gene expression along the A-P axis |
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In fish, amphibians, birds and mammals, the forelimb buds are found at the most anterior expression region of _____, the position of the first _________
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Hoxc-6
first thoracic vertebrae |
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How does the limb field regulate for lost or added parts?
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Early in developement , the limb field can regulate for lost or added parts, the excision and relocation of half a limb field will generate a complete new limb
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Where does the signal for limb bud formation come from?
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Lateral plate mesoderm
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What does the lateral plate mesoderm cells become?
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Prospective limb skeleton
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What does the lateral plate mesoderm cells secrete during early limb bud development?
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Fgf10
- it is capable of initiating limb-forming interactions b/t ecto and mesoderm |
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T/F FGF10 is initially expressed throughout the lateral plate mesoderm
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T
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How is FGF 10 restricted to limb bud sites in the lateral plate mesoderm?
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WNT formation.
Wnt2B in chick forelimb region and WNT8C in hindlimb area |
