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Unformatted text preview: MESSAGE The positional information of the Drosophila A–P axis is generated by protein gradients. The gradients ultimately depend on diffusion of newly translated protein from localized sources of specific mRNAs anchored by their 3 UTRs to ends of cytoskeletal filaments. Studying the BCD gradient How do we know that molecules such as BCD and HB-M contribute A–P positional information? Let’s consider the example of BCD in detail. 1. Genetic changes in the bcd gene alter anterior fates. Embryos derived from mothers that are homozygous for bcd null mutants lack anterior segments (Figure 18-12). If, on the other hand, we overexpress bcd in the mother, by increasing the number of copies of the bcd gene from the normal two to three, four, or more, we “push” fates that ordinarily appear in anterior positions into increasingly posterior zones of the resulting embryos, as shown in Figure 18-13. The position of the cephalic furrow (a normal feature of the embryo) serves as an example in Figure 18-13.embryo) serves as an example in Figure 18-13....
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.
- Spring '08