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ew Insert Format ToolsTable Window Help Layout Referonces Mailings Roviow View 12 15-Q10: When Sperry and colleagues ablated the posterior (temporal) RGCs, the remaining anterior (nasal) RGCs projected to the posterior tectum. Is this definitive evidence that these neurons are programmed early in development to project only to that part of the brain? Briefly explain your reasoning. 15-Q11: Netrin was first discovered in a biochemical assay for the attraction of vertebral commissural axons to floor plate. In mutants for the worm netrin homologue Unc6, sensory axons failed to project ventrally and motor neurons fail to project dorsally What does that result suggest for the role of Unc6 in axon guidance? Focus

Explanation / Answer

15-Q10)

ans) During embryonic period, the primary retina is formed. Here some photoreceptor, bipolar cells and RGCss are differentiated but there is no horizontal or amacrine cells. Therefore visual information cannot be processed.  

The definitive evidence came from molecular fingerprinting Rx, Gi, and c-opsin in its photoreceptor cells. .

15-Q11)

ans) Commisural neurons like netrins and migrate ventrally and cross over the body. The floor plate secrets a Netrin-1 (gradient ), and the lower region of the spinal cord secretes netrin-2 (gradient). The commisural neurons first encountera gradient of netrin-2, which brings them closer to the steeper netrin-1 gradient. Upon reaching floor plate, contact guidance from the floor plate cells cause axons to change directions.  

In wildtype, UNC-6 induces axons from certain centrally located sensory neuron move ventrally while inducing ventrally placed motor neurons to extend axons dorsally. In loss of function mutations, neither of these axonal movement occur.

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