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Unformatted text preview: location. Molecular biologists today are studying the role of specific protein and mRNA gradients that serve to orient differentiating cells. A substance diffusing from a shoot apex may signal other cells information about distance from the apex needed for differentiation. Radial position can be determined by radial diffusion from outermost cells. Polarity, from the first division of the zygote, determines shoot versus root in the plant axis. Gradients can act differently in root and in shoot tissues. The roles of specific genes, including plant homeotic genes, are actively being investigated. For example, homeotic genes control the degree of leaflet development. Multiple Leaflets caused by mutant homeotic gene activity...
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- Fall '09